materials Article
Unusually Small Thermal Expansion of Ordered Perovskite Oxide CaCu3Ru4O12 with High Conductivity Akihiro Tsuruta 1, * , Katsuhiro Nomura 1 , Masashi Mikami 1 , Yoshiaki Kinemuchi 1 , Ichiro Terasaki 1,2 , Norimitsu Murayama 3 and Woosuck Shin 1 1
2 3
*
National Institute of Advanced Industrial Science and Technology (AIST), Shimo-Shidami, Moriyama-ku, Nagoya 463-8560, Japan;
[email protected] (K.N.);
[email protected] (M.M.);
[email protected] (Y.K.);
[email protected] (I.T.);
[email protected] (W.S.) Department of Physics, Nagoya University, Furo-cho, Chuikusa-ku, Nagoya 464-8602, Japan National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8565, Japan;
[email protected] Correspondence:
[email protected]; Tel.: +81-52-736-7481
Received: 16 August 2018; Accepted: 5 September 2018; Published: 7 September 2018
Abstract: We measured the coefficient of thermal expansion (CTE) of conducting composite ceramics 30 vol.% CuO-mixed CaCu3 Ru4 O12 together with CaCu3 Ru4 O12 and CuO. Although conducting ceramics tend to show higher CTE values than insulators, and its CTE value does not match with other ceramic materials, the CTE of CaCu3 Ru4 O12 (7–9 × 10−6 /K) was as small as those of insulators such as CuO (9 × 10−6 /K), alumina (8 × 10−6 /K), and other insulating perovskite oxides. We propose that the thermal expansion of CaCu3 Ru4 O12 was suppressed by the Cu-O bond at the A-site due to the Jahn–Teller effect. This unusually small CTE of CaCu3 Ru4 O12 compared to other conducting oxides plays a vital role enabling successful coating of 30 vol.% CuO-mixed CaCu3 Ru4 O12 thick films on alumina substrates, as demonstrated in our previous study. Keywords: ceramics heater; conducting oxide; perovskite; thermal expansion
1. Introduction The coefficient of thermal expansion (CTE) and matching the thermal expansion between different materials are important factors when processing brittle ceramic materials that require high sintering temperatures. Currently, in order to use the heat resistance and functions of ceramic materials, devices containing heterogeneous ceramics with ceramic/ceramic or metal/ceramic interfaces have been actively developed using cofiring [1,2], printing [3,4], and coating [5–10] processes in various industrials fields, including energy [11–13], automotive [14,15], and healthcare [16,17]. Since the target ceramic materials are rarely well-sintered at the desired position when sintered with other materials, the thermal expansion needs to be tailored by optimizing the process, adding complementary materials, or controlling the composition of the ceramic [18,19]. In the case of devices using functional materials, such as perovskite oxides with CTE values often higher than those of other oxides, their thermal expansion behavior has been extensively investigated. When the perovskite composition is modified by the addition of other materials for thermal expansion matching, the properties of the original material may be degraded. We have focused on the conducting oxide CaCu3 Ru4 O12 [20–24] as an alternative conducting material to replace Pt in various high-temperature electrical devices, such as gas sensors [16] and solid oxide fuel cells [25], and have studied its physical properties and processing [26,27]. CaCu3 Ru4 O12 is an ordered perovskite oxide, the crystal structure of which is shown in the schematic diagram in Figure 1a. Materials 2018, 11, 1650; doi:10.3390/ma11091650
www.mdpi.com/journal/materials
Materials 2018, 11, x FOR PEER REVIEW Materials 2018, 11, 1650
2 of 10 2 of 9
diagram in Figure 1a. The resistivity is lower than 1 m·Ωcm, even at 500 °C, and the temperature dependence shows metallic behavior, which is rarely seen in oxides, as shown in Figure 1b (black The resistivity is lower than 1 m·Ωcm, even at 500 ◦ C, and the temperature dependence shows metallic plot). Although CaCu3Ru4O12 is difficult to sinter, we overcame this drawback by adding CuO as a behavior, which is rarely seen in oxides, as shown in Figure 1b (black plot). Although CaCu3 Ru4 O12 is sintering additive, which enabled the fabrication of dense bulks and thick films on alumina substrates difficult to sinter, we overcame this drawback by adding CuO as a sintering additive, which enabled [26]. The temperature dependences of the resistivity of 20 vol. % CuO-mixed CaCu3Ru4O12 bulk and the fabrication of dense bulks and thick films on alumina substrates [26]. The temperature dependences thick film are shown in Figure 1b. The thick film showed resistivity as low as the bulk sample. of the resistivity of 20 vol.% CuO-mixed CaCu3 Ru4 O12 bulk and thick film are shown in Figure 1b. Scanning Electron Microscope (SEM) images of the thick film are shown in Figure 1c–e, where The thick film showed resistivity as low as the bulk sample. Scanning Electron Microscope (SEM) CaCu3Ru4O12 grains were firmly bound to adjacent CaCu3Ru4O12 grains and to the alumina substrate images of the thick film are shown in Figure 1c–e, where CaCu3 Ru4 O12 grains were firmly bound without cracks and peeling. Recently, we tried to fabricate a SnO2 gas sensor using CuO-mixed to adjacent CaCu3 Ru4 O12 grains and to the alumina substrate without cracks and peeling. Recently, CaCu3Ru4O12 thick films as electrodes and heater instead of Pt on an alumina substrate [28]. Our trial we tried to fabricate a SnO2 gas sensor using CuO-mixed CaCu3 Ru4 O12 thick films as electrodes successfully showed similar sensing performance as the sensor using Pt. In addition, CuO-mixed and heater instead of Pt on an alumina substrate [28]. Our trial successfully showed similar sensing CaCu3Ru4O12 thick film heaters on alumina substrates were robust against thermal shock and rapid performance as the sensor using Pt. In addition, CuO-mixed CaCu3 Ru4 O12 thick film heaters on thermal cycling. alumina substrates were robust against thermal shock and rapid thermal cycling.
(a)
(c)
2.0 Resistivity, ρ [mΩcm]
20 vol.% CuO-mixed CaCu3Ru4O12 1.5
Thick film Bulk
1.0 CaCu3Ru4O12 Bulk 0.5
0.0
0
100
200 300 400 500 Temperature, T [oC]
(b)
600
700
(d)
(e)
Figure 1.1. (a) 3Ru 4O Temperature dependence of the resistivity of a Figure (a) Crystal Crystal structure structureofofCaCu CaCu O.12(b) . (b) Temperature dependence of the resistivity 3 Ru 4 12 3Ru4O 12 4bulk, a 20a vol. % CuO-mixed 3Ru 4O412O12 bulk, and % CuO-mixed CuO-mixed CaCu of a CaCu O12 bulk, 20 vol.% CuO-mixedCaCu CaCu bulk, anda a2020vol. vol.% 3 Ru 3 Ru Ru44O12 12 thick image of of aa 20 20vol.% vol. %CuO-mixed CuO-mixedCaCu CaCu 3Ru 4O thick CaCu33Ru CaCu thick film. (c) Cross-sectional SEM image 3 Ru 4O 1212 thick film film on onan analumina aluminasubstrate. substrate. (d) (d) and and (e) (e) are are magnified magnified images images of of the the film filmand andthe thefilm–substrate film–substrate interface, interface,respectively, respectively,shown showninin(c). (c).
We and CuO Weobserved observedthat thatCaCu CaCu3 3Ru Ru44O O12 12 and CuO can can be be easily easily compounded, compounded, and and the the composite composite thick thick film onon anan alumina substrate without anyany cracks. We further observed that filmshowed showedexcellent excellentsintering sintering alumina substrate without cracks. We further observed the thick film heater showed excellent durability against rapid heat cycles. All these findings were that the thick film heater showed excellent durability against rapid heat cycles. All these findings truly for a conventional ceramicceramic device. device. Hence, in this study, investigated the thermal wereunexpected truly unexpected for a conventional Hence, in thiswe study, we investigated the expansion of CaCu3of Ru CuO, CuO-mixed CaCu3CaCu Ru4 O312 to clarify the reason for 4 O123,Ru thermal expansion CaCu 4O12,and CuO, and CuO-mixed Ruin 4Oorder 12 in order to clarify the reason the properties of our ceramic device. In addition, we we compared the the thermal expansion of for excellent the excellent properties of our ceramic device. In addition, compared thermal expansion CaCu O12 that of of other perovskite oxides. 3 Ru34Ru of CaCu 4Owith 12 with that other perovskite oxides. 2.2. Experimental Experimental CaCu O12 was prepared prepared via 12 was CaCu33Ru Ru44O via aa solid-state solid-state reaction reaction [22,26,29]. [22,26,29]. Stoichiometric Stoichiometric mixtures mixtures of of ◦ CaCO , CuO, and RuO were pressed into pellets and calcined in air at 1000 C for 48 h. The pellets 3 2 CaCO3, CuO, and RuO2 were pressed into pellets and calcined in air at 1000 °C for 48 h. The pellets
Materials 2018, 11, 1650 Materials 2018, 11, x FOR PEER REVIEW
3 of 9 3 of 10
covered by by aa mixture mixture of of excess excess CaCO CaCO33, CuO, CuO, and and RuO RuO22 powders to prevent Ru sublimation sublimation were covered sintering and and subsequent subsequentdeviations deviationsfrom fromthe thedesired desiredcomposition. composition.The TheCaCu CaCu33Ru Ru44O O12 12 powder during sintering obtained via via mechanical mechanical grinding grinding and and ball-milling ball-milling of of the the calcined calcined pellets. pellets. was obtained CaCu33Ru44O The CaCu O1212powder powderwas was then then mixed mixed with with CuO CuO powder powder (as a sintering additive), then pressed into a pellet and sintered sintered at at 1000 1000 ◦°C air. The CuO volume fraction in the bulk was pressed C for 48 h in air. vol. %corresponding corresponding to 29.5 wt.The %. volume The volume fraction was calculated using the molecular 30 vol.% to 29.5 wt.%. fraction was calculated using the molecular weights weights and lattice constants of eachAmaterial. CuO bulk sample was obtainedaby calcining and lattice constants of each material. CuO bulkAsample was obtained by calcining pressed pelleta pressed pellet of CuO powder under the same conditions as the 30 vol. % CuO-mixed CaCu 3 Ru 4O12 of CuO powder under the same conditions as the 30 vol.% CuO-mixed CaCu3 Ru4 O12 bulk sample. bulkrelative sample.densities The relative the 30 vol. CaCu % CuO-mixed CaCu 3Rubulk 4O12 and CuOwere bulk 73% samples The of thedensities 30 vol.%ofCuO-mixed CuO samples and 3 Ru4 O12 and were respectively. 73% and 92%, respectively. 92%, (XRD) of of the the CaCu CaCu33Ru Ru44O12 X-ray diffraction (XRD) powder was was performed performed using a standard 12 powder diffractometer with parallel-beam optics of of Cu Cu Kα Kα radiation radiation in in the the 2θ-θ 2θ-θ scan mode (X’Pert Pro MPD, Malvern Panalytical, Malvern, UK) at 25, 100, 200, 300, 400, 500, 600, 700, 800, and 900 ◦°C C using a reactor chamber chamber (XRK900, (XRK900, Anton Anton Paar, Paar,Graz, Graz, Austria) Austria)in in air air [30]. [30]. The XRD patterns at all temperatures reactor analyzed using the Rietveld Rietveld method [31] and we we calculated calculated the lattice lattice constants constants using the were analyzed reported space group and crystal structural parameters as the initial value [32]. The % The CTEs CTEsof of30 30vol. vol.% thermomechanical CuO-mixed CaCu33Ru Ru44O O1212and andCuO CuObulk bulksamples samples were were measured measured in air using aa thermomechanical Plus EVO2, EVO2, Rigaku, Rigaku, Tokyo, Tokyo,Japan). Japan). analyzer (TMA; Thermo Plus 3. Results and Discussion
20
30
40
50 60 2θ [degrees]
70
80
622
521 440 442 350 532 260
510
240
332
330
321
222
310
211
200
400
422
Intensity [arb. unit]
220
◦ C. Figure 2 shows powder measured measured at at 25 °C. shows the the XRD XRD pattern pattern for forCaCu CaCu33Ru Ru44O12 All peaks were 12 powder well-indexed to those of CaCu Ru O [32] and no heterogeneous or impurity phases were identified. identified. well-indexed to those of CaCu33 4 12 12[32] and no heterogeneous or impurity phases were Figure 3a shows calculated from from powder powder XRD, plotted as a shows the the lattice lattice constant constant of of CaCu CaCu33Ru Ru44O12 12 calculated function of temperature. temperature. CaCu CaCu3Ru Ru O belongs to a large family of ordered perovskites described belongs to a large family of ordered perovskites described by 3 4O 4 1212 by general formula AC B12 , and consideredasasaafourfold fourfold superstructure superstructure of of the ABO thethe general formula AC 3B43O , 12 and cancan bebe considered ABO33 4O perovskite perovskite shown shown in Figure 1a. The lattice constant increased with increasing temperature, indicating positive thermal expansion, similar to other other conventional conventional oxide oxide materials. materials. The plot represents the lattice constant a for the cubic structure, from which the relative thermal expansion and CTE values were were evaluated. evaluated.
90
◦ C. Figure2.2.X-ray X-raydiffraction diffraction(XRD) (XRD)(CuKα) (CuKα)pattern patternof ofCaCu CaCu33Ru Ru44O12 12 powder Figure powder measured measured at at 25 25 °C.
Considering the potential applications of the perovskite, the thermal expansion should be evaluated using TMA. However, had to to be calculated from the lattice However, here here the theCTE CTEof ofCaCu CaCu33Ru Ru44O12 12 had constant because CaCu O1212could couldnot notbe be fully fully sintered. sintered. Figure Figure 3b 3b shows the thermal expansion CaCu33Ru44O expansion relative to the value at 25 °C (ΔL/L25) for the 30 vol. % CuO-mixed CaCu3Ru4O12 and CuO bulk samples measured using TMA, together with that of CaCu3Ru4O12 calculated from the data shown in
Materials 2018, 11, 1650
4 of 9
Materials 2018, 11, x FOR PEER REVIEW relative to the value at 25 ◦ C (∆L/L
4 of 10
25 )
for the 30 vol.% CuO-mixed CaCu3 Ru4 O12 and CuO bulk samples measured using TMA, together with that 3of from the data shown25 in 3 RuCuO 4 O12 calculated Figure 3a. The thermal-expansion curves of CaCu RuCaCu 4O12 and were nearly identical between Figure curves CaCu and CuO identical 3 Ru4 Oof 12 30 °C and 3a. 900The °C. thermal-expansion Hence, we concluded thatofthe addition vol. % were CuO nearly to CaCu 3Ru4O12 between did not ◦ C and 900 ◦ C. Hence, we concluded that the addition of 30 vol.% CuO to CaCu Ru O did not 25 4 12 significantly affect thermal-expansion behavior, although a detailed analysis was not 3performed [33]. significantly affect thermal-expansion a detailed analysis was not at performed [33]. This good thermal-expansion match is behavior, the reasonalthough that no serious cracks or exfoliation the interface This good thermal-expansion match the reason thatcomposite no seriousmaterial; cracks orthis exfoliation theresults interface between CaCu 3Ru4O12 and CuO wereisobserved in the supportsatthe of between CaCu Ru O and CuO were observed in the composite material; this supports the results 3 4 where 12 our previous study we successfully used CuO as a sintering additive for CaCu3Ru4O12 [26]. of our previous where successfullydependence used CuO asofa sintering 3 Ru 4 O12 [26]. Figure 3cstudy shows thewe temperature the CTEadditive of the for 30 CaCu vol. % CuO-mixed Figure 3c shows the temperature dependence of the CTE of the 30 vol.% CuO-mixed CaCu 3 RuCTE 4 O12 CaCu3Ru4O12 bulk, CuO bulk, and CaCu3Ru4O12 samples. The dotted and broken lines show the ◦ C of bulk, CuO bulk, and CaCu Ru O samples. The dotted and broken lines show the CTE at 400 4 2, 12 at 400 °C of alumina and 3ZrO respectively, for comparison, as they are widely used ceramic alumina and ZrO2 , respectively, for comparison, as they widely used materials. substrate materials. Although the ΔL/L25 of the threeare materials wereceramic almostsubstrate the same at all Although the ∆L/L of the three materials were almost the same at all temperatures, the CTEs, 25 temperatures, the CTEs, which are generally calculated as the differential value of ΔL/L25, which were are generally calculated as differential value of ∆L/LThe especially around 25 , were slightly different, especiallythe around room temperature. CTE slightly curve ofdifferent, the 30 vol. % CuO-mixed room3temperature. CTE curve of the 30between vol.% CuO-mixed bulkCaCu sample 4 O12 CaCu Ru4O12 bulk The sample was located those of CaCu CuO 3 Ru bulk and 3Ruwas 4O12 located at all between those of CuO bulk and CaCu Ru O at all temperatures, showing an acceptable 3 4 12value. The 30 vol. % CuO-mixed CaCu3Ru4Oaverage temperatures, showing an acceptable average 12 bulk value. The 30 vol.% CuO-mixed CaCu O12 bulk sample almost the same value as 3 Ru4as sample showed almost the same CTE value alumina. Thus, showed in our previous study, theCTE CuO-mixed alumina. Thus, in our previous study, the CuO-mixed CaCu Ru O thick film was successfully coated 3 4 12 CaCu3Ru4O12 thick film was successfully coated and sintered on alumina substrates without cracking and sintered on alumina substrates without cracking or peering due to this good CTE match. or peering due to this good CTE match. 7.50
(a)
CaCu3Ru4O12 (XRD) Lattice constant [Å ]
7.48 7.46 7.44 7.42 7.40 1.0
(b)
30vol.% CuO-mixed CaCu3Ru4O12 CaCu3Ru4O12 (XRD)
ΔL / L [%]
0.8
CuO
0.6 0.4 0.2 0.0 12
ZrO2
10
CTE, α [x10
-6 o
-1
C ]
(c)
8
Alumina
6 4 2 0
0
200
400 600 Temperature, T [oC]
800
1000
Figure Figure 3. 3. (a) (a) Lattice Lattice constant constant of of CaCu CaCu33Ru Ru44OO1212 asas aa function function of of temperature. temperature. (b) (b) Temperature Temperature 25 and (c) temperature dependence of the CTE of the 30 vol. % CuO-mixed dependence of ΔL/L dependence of ∆L/L25 and (c) temperature dependence of the CTE of the 30 vol.% CuO-mixed 4O12 bulk, CuO bulk, and CaCu3Ru4O12 samples. Data for the 30 vol. % CuO-mixed CaCu CaCu3Ru 3 Ru4 O12 bulk, CuO bulk, and CaCu3 Ru4 O12 samples. Data for the 30 vol.% CuO-mixed CaCu 12 bulk and CuO bulk were measured using a thermomechanical analyzer (TMA), while CaCu33Ru Ru4O 4 O12 bulk and CuO bulk were measured using a thermomechanical analyzer (TMA), while 12 were calculated from powder XRD. those thosefor forCaCu CaCu33Ru Ru4O 4 O12 were calculated from powder XRD.
Inorganic materials have various favorable properties, including conductivity, dielectricity, and magnetism. The CTE (α) depends on such properties, as follows: [34] α = αvib + αelec + αmag + αfe + αvac
(1)
Materials 2018, 11, 1650
5 of 9
Inorganic materials have various favorable properties, including conductivity, dielectricity, and magnetism. The CTE (α) depends on such properties, as follows: [34] α = αvib + αelec + αmag + αfe + αvac
(1)
where αvib , αelec , αmag , αfe , and αvac correspond to the CTE due to vibrational, electronic, magnetic, ferroelectric contribution, and vacancy formation, respectively. This formula is derived considering that the CTE is the second derivative of the Gibbs energy, where functional materials have higher energies than materials without these properties. Therefore, α of a simple insulator should be the lowest among ceramic oxide materials, except for ZrW2 O8 [35] and LaCu3 Fe4 O12 [36], which show negative thermal expansion due to peculiar mechanisms, such as lattice bending and valence transitions. Since CaCu3 Ru4 O12 shows particularly high electrical conductivity compared to other perovskite oxides, its αelec and α values are expected to be larger than those of other materials. Let us compare CaCu3 Ru4 O12 with other ABO3 -type oxides; Table 1 shows the CTE, conducting behavior, B-site cation, electron orbital of the B-site cation, and the number of d-electron of various oxides. Here, we focus on simple ABO3 -type oxides in order to simplify the comparison and discussion. The CTE values were taken directly from the references, or calculated from the temperature dependence of the lattice volume. In this paper, the materials are classified as conductor or insulator using 10 Ωcm of resistivity at room temperature as a threshold. As expected, the conductors Sr0.8 La0.2 TiO3 , SrRuO3 , La0.6 Sr0.4 Fe0.2 Co0.8 O3-x , SrCoO3 , LaCoO3 , and LaCo0.5 Ni0.5 O3 show larger CTE values than materials with insulating, ferroelectric, or dielectric properties. However, the CTE of CaCu3 Ru4 O12 is remarkably small compared to other conductors. La0.6 Sr0.4 Fe0.2 Co0.8 O3−x , SrCoO3 , and LaCoO3 are used as cathode materials in solid oxide fuel cells, and many oxygen vacancies are generated at high temperature; hence, αelec. and αvac. strongly contribute to α in these materials. Table 1. CTE, conduction behavior, B-site cation, electron orbital of B-site cation, and number of d-electron of various perovskite oxide. Material MgTiO3 CaTiO3 BaTiO3 Sr0.8 La0.2 TiO3 LiNbO3 CaHfO3 LiTaO3 KTaO3 YVO3 LaCrO3 YMnO3 LaMnO3 SrRuO3 CaCu3 Ru4 O12 LaFeO3 La0.6 Sr0.4 Fe0.2 Co0.8 O3−x SrCoO3 LaCoO3 LaCo0.5 Ni0.5 O3 ErNiO3 CaSnO3
[34] [34] [34] [37] [34] [34] [34] [34] [38] [34] [34] [34] [39] [34] [19] [34] [34] [40] [41] [34]
CTE (×10−6 /K)
Conduction Behavior
B-Site Cation
Electron Orbital of B-Site Cation
Number of D-Electron
10.1 11.6 12.1 12.5 13.7 9.6 13.3 7.01 6.4 9.2 11.2 10.9 12.7 8.9 9.7 21.4 15.6 23.1 15.1 8.1 9.2
Insulator Insulator Insulator Conductor Insulator Insulator Insulator Insulator Insulator Insulator Insulator Insulator Conductor Conductor Insulator Conductor Conductor Conductor Conductor Insulator Insulator
Ti4+ Ti4+ Ti4+ Ti4+ Nb5+ Hf4+ Ta5+ Ta5+ V3+ Cr3+ Mn3+ Mn3+ Ru4+ Ru4+ Fe3+ Fe3+ , Co3+ Co4+ Co3+ Co3+ , Ni3+ Ni3+ Sn4+
3d0 3d0 3d0 3d0 4d0 5d0 5d0 5d0 3d2 3d3 3d4 3d4 4d4 4d4 3d5 3d5 , 3d6 3d5 3d6 3d6 , 3d7 3d7 4d10
0 0 0 0 0 0 0 0 2 3 4 4 4 4 5 5.8 5 6 6.5 7 10
The CTE values are quoted at 500 ◦ C; for the datasets where this value was not stated, the data were linearly extrapolated to 500 ◦ C.
The conduction behavior of the perovskite oxides correlates with the number of d-electrons in the B-site cation. Hence, CTE values are plotted as a function of the number of d-electrons in Figure 4, where the conduction behavior of each material is represented by symbols. The CTE values
Materials 2018, 11, 1650
6 of 9
of all insulators are located in the lower part of the figure, consistent with the theory expressed by Equation (1). Although the ferroelectric materials, such as BaTiO3 , LiTaO3 and LiNbO3 , are electrically insulating, they show relatively large CTE values compared to the other insulators because of structural deformations due to polarization. Almost all conductors show CTE values larger than 10 × 10−6 /K, where that of CaCu3 Ru4 O12 is surprisingly small, despite of its high electrical Materials 2018, 11, x FOR PEER REVIEW 6 of 10 conductivity. CaCu3 Ru4 O12 and SrRuO3 are closely related materials; they both show high conductivity and have occupying B-site of perovskite. the CTEand values these materials SrRuO 3 areRu closely related the materials; they both showHowever, high conductivity haveofRu occupying theare Bsignificantly different, where CaCu smaller value than simple SrRuO 3 Ruvalues 4 O12 has 3 perovskite. site of perovskite. However, the CTE ofathese materials are the significantly different, where The structural difference those materials is that Ca and Cu arestructural ordered difference at the A-site of the CaCu 3Ru4O12 has a smallerbetween value than the simple SrRuO 3 perovskite. The between 2+ normally perovskite structure in CaCu Ru O . Cu does not usually occupy the A-site because Cu those materials is that Ca and 3Cu 4are12ordered at the A-site of the perovskite structure in CaCu3Ru4O12. appears in 6usually coordination. However, Cu in CaCu is stabilized at the A-site However, owing to Cu the Cu does not occupy the A-site because Cu2+ normally in 6 coordination. 3 Ru4 O12 appears Jahn–Teller effect. CuO octahedra extend in the z-axis direction with separation of the degenerated in CaCu3Ru4O12 is stabilized at the A-site owing to the Jahn–Teller effect. CuO octahedra extend in the 2+ acts as a large cation and can occupy the A-site. eg orbital, while Cuseparation 75%can of z-axis direction with of the degenerated eg orbital, while Cu2+ actsCu as atoms a large occupy cation and the A-site CaCuCu and the75% Cu-O which stabilized lower via separation occupy thein A-site. atoms of bond, the A-site in is CaCu 3Ru4O12at , and theenergy Cu-O bond, which is 3 Ru 4 O12 , occupy of the degenerated e orbital, would be stronger than other simple bonds such as Ca-O and g stabilized at lower energy via separation of the degenerated eg orbital, would be stronger than Ru-O. other If this Cu-O in the thermal of the CaCu3in Ruthe the thermal simple bondsbond such is aspredominant Ca-O and Ru-O. If this Cu-Oexpansion bond is predominant of 4 Othermal 12 lattice,expansion expansion will similar that of expansion CuO, as shown Figureto3b. Such a contribution of Figure the A-site the CaCu3Ru 4O12be lattice, thetothermal will beinsimilar that of CuO, as shown in 3b. cation to the thermal expansion is a novel ordered perovskite and isof a ordered great advantage in Such a contribution of the A-site cation to thefeature thermalofexpansion is a novel feature perovskite material design and applications. and is a great advantage in material design and applications. 25 Conductor Insulator
LaCoO3
Conductor
La0.6Sr0.4Fe0.2Co0.8O3
CTE, α [x10-6 1/K]
20 SrCoO3
15
10
MgTiO3 CaHfO3
0
1
SrRuO3
Insulator
YMnO3 LaMnO3
LaCrO3
LaFeO3 CaSnO3
ErNiO3
CaCu3Ru4O12
KTaO3
5
LaCo0.5Ni0.5O3
LiNbO3 LiTaO3 Sr0.8La0.2TiO3 BaTiO3 CaTiO3
YVO3
2
3
4
5
6
7
8
9
10
Number of d-electron
Figure Figure4. 4.CTE CTEof ofvarious variousperovskite perovskiteoxides oxidesplotted plotted as as aa function function of of the the number number of of d-electrons. d-electrons.
Finally, we we show the heater characteristics characteristics of a 30 vol.% thick-film Finally, vol. %CuO-mixed CuO-mixedCaCu CaCu33Ru Ru44O12 12 thick-film heater on an alumina substrate realized by the unusually small thermal expansion of CaCu Ru44O12 12 heater on the unusually small thermal expansion of CaCu33Ru and CTE CTE matching matching between CaCu33Ru Ru44OO1212and andalumina. alumina.The Thethick-film thick-filmheater heaterwas wasfabricated fabricatedon on an an and alumina substrate (3.0 × 25 ××0.3 0.3mm) mm)by byscreen-printing screen-printing aa paste paste of CuO and CaCu powders alumina × 25 CaCu33Ru44O12 12 powders mixed in in aa suitable suitable vehicle. vehicle. Figure Figure 5a 5a shows shows aa photograph photograph and and aa thermal-camera thermal-cameraimage imagewhile while32 32 V V mixed DC voltage voltage was was applied applied to to the the 30 30 vol. vol.% thick-filmheater. heater. The Themeandering meandering DC % CuO-mixed CuO-mixed CaCu CaCu33Ru44O12 12thick-film heaterpattern patterngenerates generatesheat heatup uptoto600 600 due Joule heating. Figure 5b shows the temperature heater °C◦ C due to to Joule heating. Figure 5b shows the temperature (T), (T), defined as the maximum temperature over heater pattern functionofofthe the applied applied defined as the maximum temperature over thethe heater pattern in in airairasasa afunction voltage. The Thetemperature temperatureincreased increasedlinearly linearlywith withapplied appliedvoltage, voltage,expressed expressedasasT T= = 23.4 − 146 voltage. 23.4 VV − 146 in in units of degrees Celsius; this linear V-T characteristic indicates good temperature controllability units of degrees Celsius; this linear V-T characteristic indicates good temperature controllability of of the heater. temperature ofheater the heater under V pulses, a width 10ascycle and alength cycle the heater. TheThe temperature of the under 32.0 V32.0 pulses, with awith width of 10 s of and length 20 s, is in shown in 5c. Figure The temperature increased immediately fromtemperature room temperature of 20 s, of is shown Figure The 5c. temperature increased immediately from room when ◦ C within when the voltage was applied, reaching s. The heater temperaturefollowed followedthe thecyclic cyclic the voltage was applied, reaching 600 600 °C within 9 s.9 The heater temperature voltage pulses pulses without without degradation, degradation, and and the the performance performance was was maintained maintained after after many many cycles. cycles. ItIt is is voltage clear from these results that the 30 vol. % CuO-mixed CaCu3Ru4O12 thick-film heater on an alumina substrate is surprisingly robust and is thought to be reliable enough to be used as a substitute for Pt as a conducting material for various electrical devices.
Materials 2018, 11, 1650
7 of 9
clear from these results that the 30 vol.% CuO-mixed CaCu3 Ru4 O12 thick-film heater on an alumina substrate is surprisingly robust and is thought to be reliable enough to be used as a substitute for Pt as Materials 2018, 11, x FOR PEER REVIEW 7 of 10 a conducting material for various electrical devices. 700 30 vol.% CuO-mixed CaCu3Ru4O12
Temperature, T [oC]
600
Thick film heater
500 400 300 200 100 in Air 0
0
5
(a)
T = 23.4 V -146 10
15 20 25 Voltage, V [V]
Temperature, T [oC]
35
(b)
700
Voltage
30
in Air
600 500 400 300 200 100 0 on off 0
50
100
150
200 250 Time, t [s]
300
350
400
(c) Figure5.5.(a) (a)Photograph Photographofofthe the3030vol.% vol. % CuO-mixed CaCu 3RuO thick-filmheater heateron onthe thealumina alumina Figure CuO-mixed CaCu 3 Ru 4 4O 1212thick-film substrateand and a thermal-camera image an applied voltage 32 (b) V DC. (b) Temperature (T), substrate a thermal-camera image withwith an applied voltage of 32 VofDC. Temperature (T), defined defined as the maximum temperature over the meandering heater pattern, as a function of the applied as the maximum temperature over the meandering heater pattern, as a function of the applied voltage. voltage. (c) Temperature of the heater under 32.0 V pulses with of a width of 10 s and cycle time (c) Temperature of the heater under cyclic 32.0cyclic V pulses with a width 10 s and cycle time of 20 s. of experiments 20 s. All experiments were performed All were performed in air. in air.
4.4.Conclusions Conclusions We CuO-mixed CaCu 3 Ru 4O 1212and Wemeasured measuredthe theCTE CTEofof3030vol.% vol. % CuO-mixed CaCu 3Ru 4O andCuO CuObulk bulksamples samplesusing usingTMA TMA and from the lattice constant determined using high-temperature 3 Ru 4O 12 andcalculated calculatedthe theCTE CTEofofCaCu CaCu 3Ru 4O 12 from the lattice constant determined using high-temperature ◦ XRD The ∆L/L of these materials were nearly identical and 25these XRD measurements. measurements. The ΔL/L 25 of materials were nearly identical betweenbetween 25 °C and25900C°C; we ◦ 900 C; we measured the values for CaCu Ru O , CuO, and 30 vol.% CuO-mixed CaCu Ru O of−1, 3 and 4 1230 vol. % CuO-mixed CaCu3Ru4O12 of 8.27 3 × 410−6 12 K measured the values for CaCu3Ru4O12, CuO, − 6 − 1 − 6 − 1 − 6 − 1 ◦ 8.27 , 9.59 ××10 K−1, respectively, , and 8.60 × at 10500K respectively, at 500 C. These values were −1, and 9.59×× 10 10−6 KK 8.60 10−6 K °C. ,These values were similar to those of alumina −6 K−1 ). The CTE matches between CaCu Ru O /CuO and similar to those of alumina (8.0 × 10 −6 −1 3 4 %12 CuO-mixed (8.0 × 10 K ). The CTE matches between CaCu3Ru4O12/CuO and 30 vol. 30 vol.% CuO-mixed CaCu3 Ru4the O12 /alumina the successful compounding coating of CaCu 3Ru4O12/alumina explain successful explain compounding and coating of theseand material pairs these material pairs in The our CTE previous study. The CTE of CaCu Ru4 Oof12other is smaller than demonstrated in ourdemonstrated previous study. of CaCu 3Ru4O12 is smaller than3 that conducting that of other conducting perovskite oxides, and close to the values for insulating perovskite oxides. perovskite oxides, and close to the values for insulating perovskite oxides. The unusually small CTE of The unusually small CTE of CaCu Ru4 Oinfluence to occupying be due to the of Cu occupying 12 is thought CaCu 3Ru4O12 is thought to be due 3to the of Cu theinfluence A-site of the perovskite viathe the A-site of the perovskite via the Jahn–Teller effect. Such a contribution of the A-site cation in the ordered Jahn–Teller effect. Such a contribution of the A-site cation in the ordered perovskite material to the perovskite material to the thermal expansion offers a novelinand superior advantage in material design thermal expansion offers a novel and superior advantage material design and applications. and applications. Author Contributions: A.T., I.T., and W.S. conceived and designed the experiments; A.T. performed the experiments; K.N. measured and analyzed high-temperature XRD; A.T., I.T., and W.S. analyzed the data; M.M., Y.K., and N.M. helped with the experiments and discussed the results; A.T. wrote the paper. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest.
References.
Materials 2018, 11, 1650
8 of 9
Author Contributions: A.T., I.T., and W.S. conceived and designed the experiments; A.T. performed the experiments; K.N. measured and analyzed high-temperature XRD; A.T., I.T., and W.S. analyzed the data; M.M., Y.K., and N.M. helped with the experiments and discussed the results; A.T. wrote the paper. Funding: This research received no external funding. Conflicts of Interest: The authors declare no conflict of interest.
References 1.
2.
3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
14. 15. 16.
17. 18. 19.
20.
Gongora-Rubio, M.R.; Espinoza-Vallejos, P.; Sola-Laguna, L; Santiago-Avilés, J.J. Overview of low temperature co-fired ceramics tape technology for meso-system technology (MsST). Sens. Actuators A 2001, 89, 222–241. [CrossRef] Miyazaki, H.; Iwakiri, S.; Hirao, K.; Fukuda, S.; Izu, N.; Yoshizawa, Y.; Hyuga, H. Effect of high temperature cycling on both crack formation in ceramics and delamination of copper layers in silicon nitride active metal brazing substrates. Ceram. Int. 2017, 43, 5080–5088. [CrossRef] Jean, J.H.; Chang, C.R.; Chen, Z.C. Effect of Densification Mismatch on Camber Development during Cofiring of Nickel-Based Multilayer Ceramic Capacitors. J. Am. Ceram. Soc. 1997, 80, 2401–2406. [CrossRef] Niimi, H.; Mihara, K.; Sakabe, Y.; Kuwabara, M. Preparation of Multilayer Semiconducting BaTiO3 Ceramics Co-Fired with Ni Inner Electrodes. Jpn. J. Appl. Phys. 2007, 46, 6715–6718. [CrossRef] Park, J.H.; Akedo, J.; Sato, H. High-speed metal-based optical microscanners using stainless-steel substrate and piezoelectric thick films prepared by aerosol deposition method. Sens. Actuators A 2007, 135, 86–91. [CrossRef] Akedo, J.; Lebedev, M. Piezoelectric properties and poling effect of Pb(Zr, Ti)O3 thick films prepared for microactuators by aerosol deposition. Appl. Phys. Lett. 2000, 77, 1710–1712. [CrossRef] Iijima, Y.; Tanabe, N.; Kohno, O.; Ikeno, Y. In-plane aligned YBa2 Cu3 O7−x thin films deposited on polycrystalline metallic substrates. Appl. Phys. Lett. 1992, 60, 769–771. [CrossRef] Kakimoto, K.; Iijima, Y.; Saitoh, T. Fabrication of long-Y123 coated conductors by combination of IBAD and PLD. Physica C 2003, 392–396, 783–789. [CrossRef] Doi, T.; Hashimoto, M.; Horii, S.; Ichinose, A. Fabrication of YBa2 Cu3 O7 Superconducting Film on {100} Textured Cu Tape via Conductive Buffer Layers. Mater. Trans. 2017, 58, 1493–1499. [CrossRef] Ichinose, A.; Horii, S.; Doi, T. Possibility of the material cost reduction forward developing low-cost 2nd generation superconducting wires. Jpn. J. Appl. Phys. 2017, 56, 103101. [CrossRef] Tucker, M.C.; Lau, G.Y.; Jacobson, C.P.; DeJonghe, L.C.; Visco, S.J. Performance of metal-supported SOFCs with infiltrated electrodes. J. Power Sources 2007, 171, 477–482. [CrossRef] Tucker, M.C. Progress in metal-supported solid oxide fuel cells: A review. J. Power Sources 2010, 195, 4570–4582. [CrossRef] Nagaya, S.; Watanabe, T.; Tamada, T.; Naruse, M.; Kashima, N.; Katagiri, T.; Hirano, N.; Awaji, S.; Oguro, H.; Ishiyama, A. Development of High Strength Pancake Coil With Stress Controlling Structure by REBCO Coated Conductor. IEEE Trans. Appl. Supercond. 2013, 23, 4601204. [CrossRef] Gérard, B. Application of thermal spraying in the automobile industry. Surf. Coat. Technol. 2006, 201, 2028–2031. [CrossRef] Song, R.G. Hydrogen permeation resistance of plasma-sprayed Al2 O3 and Al2 O3 –13wt.% TiO2 ceramic coatings on austenitic. Surf. Coat. Technol. 2003, 168, 191–194. [CrossRef] Itoh, T.; Miwa, T.; Tsuruta, A.; Akamatsu, T.; Izu, N.; Shin, W.; Park, J.; Hida, T.; Eda, T.; Setoguchi, Y. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns. Sensors 2016, 16, 1891. [CrossRef] [PubMed] Itoh, T.; Nakashima, T.; Akamatsu, T.; Izu, N.; Shin, W. Nonanal gas sensing properties of platinum, palladium, and gold-loaded tin oxide VOCs sensors. Sens. Actuators B 2013, 187, 135–141. [CrossRef] Takenaka, K. Negative thermal expansion materials: Technological key for control of thermal expansion. Sci. Technol. Adv. Mater. 2012, 13, 013001. [CrossRef] [PubMed] Ullmann, H.; Trofimenko, N.; Tietz, F.; Stöver, D.; Ahmad-Khanlou, A. Correlation between thermal expansion and oxide ion transport in mixed conducting perovskite-type oxides for SOFC cathodes. Solid State Ion. 2000, 138, 79–90. [CrossRef] Labeau, M.; Bochu, B.; Joubert, J.C.; Chenavas, J. Synthèse et caractérisation cristallographique et physique d’une série de composés ACu3 Ru4 O12 de type perovskite. J. Solid State Chem. 1980, 33, 257–261. [CrossRef]
Materials 2018, 11, 1650
21. 22. 23. 24. 25.
26.
27.
28.
29. 30. 31. 32.
33. 34. 35. 36.
37. 38. 39. 40.
41.
9 of 9
Subramanian, M.A.; Sleight, A.W. ACu3 Ti4 O12 and ACu3 Ru4 O12 perovskites: High dielectric constants and valence degeneracy. Solid State Sci. 2002, 4, 347–351. [CrossRef] Kobayashi, W.; Terasaki, I.; Takeya, J.; Tsukada, I.; Ando, Y. A Novel Heavy-Fermion State in CaCu3 Ru4 O12 . J. Phys. Soc. Jpn. 2004, 73, 2373–2376. [CrossRef] Tran, T.T.; Takubo, K.; Mizokawa, T.; Kobayashi, W.; Terasaki, I. Electronic structure of CaCu3 Ru4 O12 studied by X-ray photoemission spectroscopy. Phys. Rev. B 2006, 73, 193105. [CrossRef] Juan, W.R.; Yuan, Z.Y.; Li, W.; Yong, L.; Jing, S.; Rui, X.; Feng, W.J. Growth and characterization of CaCu3 Ru4 O12 single crystal. Chin. Phys. B 2015, 24, 097501. [CrossRef] Sumi, H.; Yamaguchi, T.; Hamamoto, K.; Suzuki, T.; Fujishiro, Y.; Matsui, T.; Eguchi, K. AC impedance characteristics for anode-supported microtubular solid oxide fuel cells. Electrochim. Acta 2012, 67, 159–165. [CrossRef] Tsuruta, A.; Mikami, M.; Kinemuchi, Y.; Terasaki, I.; Murayama, N.; Shin, W. High electrical conductivity of composite ceramics consisting of insulating oxide and ordered perovskite conducting oxide. Phys. Status Solidi A 2017, 214, 1600968. [CrossRef] Tsuruta, A.; Mikami, M.; Kinemuchi, Y.; Terasaki, I.; Murayama, N.; Shin, W. Element Strategy Using Ru-Mn Substitution in CuO-CaCu3 Ru4 O12 Composite Ceramics with High Electrical Conductivity. Crystals 2017, 7, 213. [CrossRef] Tsuruta, A.; Itoh, T.; Mikami, M.; Kinemuchi, Y.; Terasaki, I.; Murayama, N.; Shin, W. Trial of an All-Ceramic SnO2 Gas Sensor Equipped with CaCu3 Ru4 O12 Heater and Electrode. Materials 2018, 11, 981. [CrossRef] [PubMed] Brizé, V.; Lambert, C.A.; Wolfman, J.; Gervais, M.; Gervais, F. Synthesis and microstructural TEM investigation of CaCu3 Ru4 O12 ceramic and thin film. J. Solid State Chem. 2011, 184, 2719–2723. [CrossRef] Nomura, K. Crystal Structure and Proton Conduction Path of Perovskite-type Oxides by Using a Laboratory X-ray Diffractometer with a Parallel Beam Optics. J. Cryst. Soc. Jpn. 2008, 50, 155–160. [CrossRef] Izumi, F.; Momma, K. Three-dimensional visualization in powder diffraction. Solid State Phenom. 2007, 130, 15–20. [CrossRef] Ebbimghaus, S.G.; Weidenkaff, A.; Cava, R.J. Structural Investigations of ACu3 Ru4 O12 (A = Na, Ca, Sr, La, Nd)—A Comparison between XRD-Rietveld and EXAFS Results. J. Solid State Chem. 2002, 167, 126–136. [CrossRef] Rosen, B.W.; Hashin, Z. Effective thermal expansion coefficients and specific heats of composite materials. Int. J. Eng. Sci. 1970, 8, 157–173. [CrossRef] Inaba, H.; Tagawa, H. Semi-Empirical Estimation of Thermal Expansion Coefficients of Perovskite-Type Oxides. J. Ceram. Soc. Jpn. 1998, 106, 272–278. [CrossRef] Mary, T.A.; Evans, J.S.O.; Vogt, T.; Sleight, A.W. Negative Thermal Expansion from 0.3 to 1050 Kelvin in ZrW2 O8 . Science 1996, 272, 90–92. [CrossRef] Long, Y.W.; Hayashi, N.; Saito, T.; Azuma, M.; Muranaka, S.; Shimakawa, Y. Temperature-induced A–B intersite charge transfer in an A-site-ordered LaCu3 Fe4 O12 perovskite. Nature 2009, 458, 60–63. [CrossRef] [PubMed] Park, B.; Lee, J.; Lee, S.; Lim, T.; Park, S.; Snog, R.; Im, W.B.; Shin, D. La-doped SrTiO3 interconnect materials for anode-supported flat-tubular solid oxide fuel cells. Int. J. Hydrogen Energy 2012, 37, 4319–4327. [CrossRef] Blake, G.R.; Palstra, T.T.M.; Ren, Y.; Nugroho, A.A.; Menovsky, A.A. Neutron diffraction, x-ray diffraction, and specific heat studies of orbital ordering in YVO3 . Phys. Rev. B 2002, 65, 174112. [CrossRef] Kennedy, B.J.; Hunter, B.A. High-temperature phases of SrRuO3 . Phys. Rev. B 1998, 58, 653. [CrossRef] Wang, X.; Han, Y.; Song, X.; Liu, W.; Jin, Y.; Liu, W.; Cui, H. An insight into the effects of transition metals on the thermal expansion of complex perovskite compounds: An experimental and density functional theory investigation. Phys. Chem. Chem. Phys. 2018, 20, 17781–17789. [CrossRef] [PubMed] Alonso, J.A.; Martínez-Lope, M.J.; Casais, M.T.; García-Muñoz, J.L.; Fernández-Díaz, M.T.; Aranda, M.A.G. High-temperature structural evolution of RNiO3 (R = Ho, Y, Er, Lu) perovskites: Change disproportionation and electronic localization. Phys. Rev. B 2001, 64, 094102. [CrossRef] © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
