Compositional inhomogeneity in Li- and Ta-modified (K, Na)NbO3 ceramics

Compositional inhomogeneity is examined in Li- and Ta-modified potassium sodium niobate (K,Na)NbO3 perovskite ceramics. The inhomogeneous distribution of the A-site (K and Na) and B-site (Nb and Ta) cations is found to be correlative. The inhomogeneity could not be eliminated by prolonged high-temperature annealing in samples prepared by direct mixing of alkaline carbonates and Ta and Nb oxides. In contrast, the precursor method, where a (NbxTa1-x)(2)O-5 solid solution was first formed, led to a considerably improved compositional homogeneity and appreciably enhanced dielectric, ferroelectric, and piezoelectric properties. Our results suggest that more attention needs to be paid toward controlling the compositional fluctuation of this complex solid solution system.