Phase Transitions in the System BaTiO 3 —KnbO 3

Solid solution formation in the system BaTiO 3 —KnbO 3 was established by X‐ray diffraction and dielectric measurements. Solid solutions with cubic symmetry were observed in the composition range from 4 to 90 mole % KnbO 3 at room temperature. The lattice parameter for the BaTiO 3 solid solutions increased with increasing KNbO 3 ; that for the KnbO 3 solid solutions decreased with the addition of BaTiO 3 . A distinct discontinuity in lattice parameter was observed at the composition containing about 65 mole % BaTiO 3 . Dielectric measurements were made from‐195° to 400°C. The cubic‐tetragonal transition temperature of BaTiO 3 was rapidly lowered with increasing addition of KNbO 3 , whereas the two lower phase transition temperatures were raised. All three phase transitions of KnbO 3 were rapidly lowered with increasing addition of BaTiO 3 . The observed phase transitions, lattice parameters, and electron probe data suggest a complex region in the subsolidus which extends from 35 to about 75 mole % KNbO 3 .