LATTICE DEFECT STUDIES OF HIGH QUALITY SINGLE CRYSTAL PLATINUM AND PALLADIUM.

Abstract

An improved quenching technique is described. This technique allows samples to be quenched at slow quenching rates without introducing unwanted dislocations during quench. High quality platinum single crystals 1 mm in diameter have been quenched from temperatures between 900°C and 1550°C using this technique. The data have been analysed and discussed using a sink model for vacancy loss proposed by Emrick. The formation energy was found to be (1.30 ± 0.03) eV. The entropy of formation and the concentration of vacancies at the melting point have been determined to be respectively (0.42 ± 0.11)k and (9.4 ± 0.7)10⁻⁴. High purity palladium single crystals have also been quenched using the same technique. Due to the need for a temperature scale, measurements of the electrical resistance of an ultra pure palladium single crystal have been made to a temperature within 100°C of the melting point. These, along with measurements of the liquid palladium resistivity, are reported. The results are discussed and compared to previously reported values.