Tuning the orthorhombic-rhombohedral phase transition temperature in sodium potassium niobate by incorporating barium zirconate

We report that the orthorhombic-rhombohedral phase transition temperature in sodium potassium niobate could be tuned from lower to higher than room temperature by incorporating barium zirconate into it. It is revealed that when barium zirconate is between 8 mol% and 15 mol%, the solid solution exhibits rhombohedral symmetry at room temperature. Rietveld analysis shows that the space group of the rhombohedral phase is Ram. It is suggested that a relatively larger B-cation favors the low-temperature phase which is a common phenomenon for perovskite ferroelectrics. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim