New Study of Defect Structure in Nonstoichiometric Lithium Tantalate

Experimental and analytical study of the Curie temperature and density for different compositions of nonstoichiometric lithium tantalate are presented in this work. Our results show that the Curie temperature decreases and the density increases linearly with increasing composition. Using the theoretical approach to the defect structure analysis, developed by Safaryan, a comparison between three defects models (oxygen vacancies, tantalate vacancies and lithium vacancies) has been proposed. The calculated and measured values show that the lithium vacancy model effectively describes the defect structure in nonstoichiometric lithium tantalate. The experimental procedures employed indicate that the errors in the formulae obtained have been estimated to be about 0.8% for Li, 1% for Ta and in the crystal parameters they have been estimated to be about 0.001 A for a and 0.005 A for c. Communicated by Dr. George W. Taylor