Defect characterization of slow-cooled and quenched samples of calcium-copper-titanate through positron annihilation spectroscopy

Abstract

Positron annihilation lifetime and Doppler-broadened gamma-ray spectra have been analyzed for slow-cooled and thermally quenched polycrystalline samples of calcium-copper-titanate. Two positron lifetimes revealing the characteristic defects in the respective samples were carefully analyzed to compare and contrast the significance of their origin and implication. A third component arising from positronium formation at the powdered particle surfaces has been considered in the analysis although its significance is lost in its very small intensity (∼ 1.1–1.2%). In the quenched sample, the defect-specific long positron lifetime (τ₂) is found to larger and the mean lifetime smaller while its intensity I₂ is found drastically smaller and the concentration of defects less by an order of magnitude as compared to the slow-cooled sample. The observed changes in electrical parameters of slow-cooled and quenched samples were found to have correlations with the positron annihilation lifetime and Doppler-broadened lineshape parameters.

Keywords:

• Calcium-copper-titanate
• defects
• positron annihilation
• quenching
• vacancies

Acknowledgments

One of the authors (PMGN) wants to convey appreciation to his students Shubharaj Mukharjee and Maudud Ahmed for their help in the analysis of the positron annihilation data.