Preparation of Y<sub>3</sub>NbO<sub>7</sub> Powders with Excess Oxygen Vacancies and Conductivity of the Sintered Bodies

Abstract

Y3NbO7 powders with excess oxygen vacancies were prepared by calcining coprecipitated powders of (YO1.5)1-x(NbO2.5)x(x=0.20-0.30) at 1200°C in an Ar gas flow, which was synthesized from YCl3 and NbCl5 using the liquid phase coprecipitation method. Also number of oxygen vacancies in the synthesized powders was estimated from the density, and conductivity of the resulting sintered bodies was measured. The number of oxygen vacancies in the Y3NbO7 powder in the x=0.25 composition synthesized in Ar was around 1.48 in unit cell even after heat treatment in air. The number of oxygen vacancies in the x=0.20 and 0.30 compositions synthesized in air increased by the change of valence number in Nb. On the other hand, after synthesizing the powder comprised of the x=0.20 composition in Ar, the number of oxygen vacancy of the powder reheated in air was 2.06. The conductivity of sintered bodies fabricated from the Y3NbO7 powders synthesized in Ar was raised by a half digit higher than that of the sintered body fabricated from the powders synthesized in air. The conductivity of the sintered bodies obtained from the synthesized powders increased almost linearly with an increase in the number of oxygen vacancies. Therefore, it was found that the introduction of oxygen vacancies by controlling composition and the powder preparation was an important factor for increasing in conductivity of Y3NbO7 sintered body.