Thermodynamic Properties of Pt — B Solid Solutions

Abstract

AbstractThe activity coefficients of B in Pt were determind at 1200 and 1300 K by equilibrating Pt with B2O3 in a controlled H2 – H2O atmosphere and measuring the weight gain. The partial molar excess Gibbs energies at vanishing B concentration are –44 and –43 kJ/ mol, respectively. The atomic fractions at the solidus line are 0.036 and 0.031. A relative lattice contraction of the solid solutions prepared at 1200 and 1300 K of (1/a)(∂a/∂xB) = −0.042 and of −0.035 ± 0.002 was observed. This dependence of the lattice constant on the temperature of preparation suggests a mixed occupation of lattice and interstitial sites, with the majority of B atoms on lattice sites.