4498833 Wafer orientation system: Richard Hertel assigned to Varian Associated Inc

Abstract

Reactions of Me2+ cations with O2− in molten (KBr + NaBr) (0.5:0.5) and (KBr + LiBr) (0.4:0.6) mixtures at T = 973 K were studied by potentiometric titration method using Pt(O2)|ZrO2(Y2O3) indicator electrode. In the former melt, the set of cations available for investigation was wide enough (Me = Sr, Ca, Mn, Co, Ni and Pb) and the corresponding solubility product indices (pKs,MeO, molalities) were found to be (3.81 ± 0.3) (SrO), (5.00 ± 0.3) (CaO), (7.85 ± 0.3) (MnO), (8.80 ± 0.1) (CoO), (9.72 ± 0.04) (NiO) and (5.20 ± 0.3) (PbO). A correlation between pKs,MeO and the polarisation action of the metal cation by Goldschmidt (ZerMe2+-2) was obtained. The oxide solubilities on the mole fraction scale were shown to be close to those obtained in molten (KCl + NaCl) equimolar mixture. On the basis of the solubility data the oxobasicity index (primary medium effect for oxide ion) for the (KBr + NaBr) melt was estimated as pI{KBr–LiBr} = −0.24. Due to considerable oxoacidic properties of Li+ cation in the molten (KBr + LiBr) eutectic, it was possible to study only three from the above cations (Me = Mn, Co and Ni) and their pKs,MeO values were (4.36 ± 0.2), (5.19 ± 0.05) and (6.25 ± 0.03), respectively. Comparison with the corresponding data for (KBr + NaBr) equimolar mixture showed that the Li+-based melt dissolved all the studied oxides in more extent. On the basis of the data obtained, the oxobasicity index value pI{KBr − LiBr} was estimated as (3.01 ± 0.5), that was close to the similar parameter of the chloride analogue (KCl + LiCl) (3.36). The change of the constituent anion of the melt in Cl− → Br− does not result in appreciable changes of the melt acidity. Oxoacidic properties of the bromide melts rise in the following sequence: (2CsBr + KBr), pIL = −1.15 → (KBr − NaBr), pIL = −0.24 → (KBr − LiBr), pIL = +3.01.