Phase Diagram of the (Na0.5K0.5)NbO3-ATiO3 Solid Solution

To elucidate mechanisms responsible for the enhanced piezoelectric properties in the potassium-sodium niobate-based solid solutions, phase diagram of the (1 − x) (Na0.5K0.5)NbO3-xATiO3 (A = Sr, Ba, and Pb) systems has been established according to the dielectric constant measurement and the crystal structure analysis results. A tetragonal/orthorhombic morphotropic phase boundary (MPB) is found around x∼ 0.05, where the piezoelectric properties were enhanced. Rietveld refinements show that the tetragonal/orthorhombic MPB is the same as that found in the lead zinc niobate-lead titanate system.