Effect of bismuth deficiency on structure and electrical properties of (Na 0.5Bi 0.5) 0.93Ba 0.07TiO 3 ceramics

Abstract

(Na 0.5Bi x ) 0.93Ba 0.07TiO 3 ( x=0.500–0.492) ceramics were prepared by a citrate method, and the structure and electrical properties of the ceramics were investigated with respect to the amount of Bi deficiency. It was detected that the Bi deficiency had a considerable impact on the crystal structure and microstructure. The inspection of both the temperature dependence of the dielectric properties (free permittivity ε 33 T/ ε 0 and dielectric loss tan δ) and the evolution of the polarization–electrical field ( P– E) hysteresis loops with measuring temperature suggests that the Bi deficiency served to increase the depolarization temperature ( T d). The Bi deficiency led to an increase in the coercive field ( E c) and mechanical quality factor ( Q m) together with a decrease in the remanent polarization ( P r) and piezoelectric constants ( d 33). The variation of the structure and electrical properties with Bi deficiency amount was qualitatively interpreted in terms of the formation of Bi and oxygen vacancies in the Bi-deficient specimens. This research indicates the importance of adequately controlling Bi stoichiometry of (Na 0.5Bi 0.5) 0.93Ba 0.07TiO 3 ceramics in obtaining the desired ferroelectric and piezoelectric properties.