Ferroelectric Phase Transitions in the System PbTiO 3 ,‐KNbO 3 ,

The formation of a complete series of solid solutions in the system PbTiO 3 ‐KNbO 3 was established by X‐ray and dielectric studies. The room‐temperature symmetry of the entire system was tetragonal except for compositions containing more than 96 mole % KNbO 3 , which had orthorhombic symmetry. The axial ratio, c/a , and the ferroelectric Curie temperature decreased from both the end‐members. The lowest Curie temperature observed in the system was 175°C for the composition with 80 mole % KNbO 3 . A generalization has been made on the variation of ferroelectric Curie temperatures with compositions in binary systems of perovskitetype solid solutions with and without a common cation.