Oxygen vacancy dependent structural phases in KNbO^sub 3

By considering the fact that oxygen vacancies are always the integral part of oxides when prepared at high temperature, variation in oxygen vacancy concentration was introduced in KNbO3 by varying calcinations temperature of precursors. A similar kind of variation was also introduced in KNbO3 by varying La3+ doping concentration. Our analysis shows that the phase formation in KNbO3 greatly responds to the variation in concentration of oxygen vacancy. It was found that, when KNbO3 bears more oxygen vacancies orthorhombic phase formation at room temperature becomes favorite otherwise cubic phase is favored. The result seems to be highly important to look insight into the mechanism of paraelectric-ferroelectric phase transition.