Phase Diagram of KF-Doped BaTiO₃ Single Crystals

Abstract

KF-doped BaTiO ₃ single crystals were grown by a KF-flux method, changing the molar ratios of the liquid-solution consisting of KF: BaO: TiO ₂ = 10: 1: 1+α where α is a variable in a range up to 1.2. By using an electron-probe micro-analyzer; the content x in the chemical formula, Ba _{1− x} K _x TiO _{3− x} F _x , was evaluated; it changes continuously from approximately 0.01 to 0.12 as α increases from 0 to 1.2. The dielectric constant was measured for these crystals with different x-values. The Curie-temperature T_C decreases monotonously from 390 K to 280 K with increasing x, while the maximum value of the dielectric constant ε_max at T_C exhibits a peak around x = 0.1 (near the tricritical point) where the transition changes the character from the first-order to the second-order. The phase-diagram of KF-doped BaTiO ₃ was determined.

Keywords:

• KF doped BaTiO₃
• single crystal
• Curie-temperature
• dielectric properties
• phase diagram

Acknowledgment

This work was supported in part by the Grant-in-Aid for Scientific Research (No. 19360299) from Japan Society for the Promotion of Science, and by the collaborative research project of Materials and Structures Laboratory, Tokyo Institute of Technology. I would like to thank Mr. Yuuta Hiraki for his assistance in the crystal growth and the dielectric measurement.