redox behavior of copper ions in fp and p

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Fluoride phosphate (FP) iand phosphate (P) glasses were doped with CuO in low. (25 - 1.000 ppm Cu) and high (10.000, 20.000, and 287.000 ppm Cu) ...
REDOX BEHAVIOR OF COPPER IONS IN FP AND P GLASSMELTS ,'-.. ,,,-.,-•,, • . . . , . - ; ^ ^ , •

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D. Ehrt and A. Brettschneider (Otto-Schott-Institut, University, D-07743 Jena, Germany) . '



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Fluoride phosphate (FP) iand phosphate (P) glasses were doped with CuO in low (25 - 1.000 ppm Cu) and high (10.000, 20.000, and 287.000 ppm Cu) concentrations, and melted under normal, strong oxidizing, and strong reducing conditions* The redox behavior of copper in glass was investigated quantitatively depending on concentration, temperature, time, and host glass by absorption and luminescence spectroscopy, optical and electron microscopy. In the VUV and UV region two Charge transfer bands of Cu1+ centered at 175 nm and 230 nm, and of Cu2+ at 185 nm and 230; nm were found. The calculated individual absorption coefficients are very high. For Cu2+ a broad d-d transition band was found at 830 - 870um causing a:bluet>r green cotor together with the UV absorption band. Cu°j CiijO colloids, and metällic copper crystals were observed too in glasses melted^under reducing conditions. In high doped glasses CujO and Cu° were aggregated on the sample surface. Jv Introduction

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Ruoride phosphate (FP) and phosphate (P) glasses are potentially good ultraviolet (UV) transmitting materials. Their intrinsic UV absorption edge has been observed in the vacuum «ultraviolet, (VUV) region at 160 r 200 n m d u e t o electron transition bands, ThevUV «dge js shifted to longer wavelength with incrcasing phosphate content [1]. However^ the measured UV transmission of glass is frequently Kmited by trace imporitieSf [2]. Beside, iron copper is one ofjthemost'important impurities^In previous ,papers; we ;have studied the effect of absorption and the redox statesiof Fe, Ni, Pb, and Ca^ in the UV-VIS-IR region in the cases of a few ppm- irtfsome detail [3^ 5}. In :this ,paper, we have studied ithe absorption of ;copper in the VUV region totf, andvthe redox behavior at low (25-1.000 ppm Cu) and high (KU)00, 20.000, and 287.000 ppniCB = Cu(PO3)2) content depending on mdlting conditionsv temperatüref time, and hoSt glass. ;.-:. •.,••;..-^ %>• ;•,:.-; ; : ^>r":;., •. •.; .. .;••;,: ; : .>r'. - ".'?*'•• ;"\''., i •••''.' ^'--' Cu1+ activated; solids are attractingrmaterials for many applications# for instance, broadband tunable solid-state lasers [6], and semiconducting glasses [7]. Glass with small Cu° colloids is interesting for non-linear optical properties/

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Experi mental

E, = ea.c.d = lg(Io/I)x

Samples of one fluoride phosphate glass composition FP 10 (10 mol% Sr(PO3)2, 35 A1F3, 30 CaFj, 15 SrF2, 10 MgFz) doped with 25, 50, 75, 100, 500, 1.000, 10.000, and 20.000 ppm Cu äs CuO were melted, at first, ,as 200 g batches in a platinum crucible under normal conditions in an air atmosphere at 1.000 - 1.050°C. Than 30 g batches were remelted under normal conditions with väried teihperatures between 900 - 1200°C for 60 min. Oxygen was bubbled through the melts in some cases achieving oxidizing conditions at the same temperatüres. For reducing conditions depending onjthe melting temperature, 30 90% Cu°

rose (Cu20) Cu1+ 85% Cü° 15% blacksurface Cu^OjCu*

bulkt c.less Cul+ 1% black '" surface Cu2O,Cuö bulk: c.less Cu1+ 1% '.'•

n: refractive index, e: X=546,07nm, F': X=479,99nm, C':X=643,85nm;

v.: dispersion coefficient = ('

[1] Ehrt D, Seeber W, J.Non-Cryst.Sol.l29(1991)19 [2] Cook L, Mader K-H, J.Amer.Ceram.Soc.65(1982)597 [3] Seeber W, Ehrt D, phys.stat.sol.(a)130(1992)K2l5 [4] Ehrt D, Seeber W, 2nd ESG 1993, Venice, Pröd321 [5] Ehrt D et al., J.Non-Cryst.SoI. 177(1994)405 [6] Liu H, Gan F, J.Lumin.40&41(1988)129 [7] Bae B, Weinberg MC, J.Appl.Phys.73(1993)7760

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