Dielectric Properties and Phase Diagram of (Sr_1-xBa_x)₂Nb₂O₇ Single Crystals

Abstract

Dielectric constants, ε_b′ and ε_c′ along the crystallographic b and c axes respectively, were measured in a temperature range of 10 − 700 K on Ba-substituted Sr₂Nb₂O₇ single crystals with different Ba concentrations up to x = 0.32. When x = 0, two dielectric anomalies were observed at T_I = 489 K and at T_L = 100 K, owing to the incommensurate phase transition and the low-temperature ferroelectric phase transition, respectively. Both T_I and T_L decrease with Ba-content x at initial slopes of ca. −19 and −37 K/mol%, respectively, and become broad at x = 0.04 and almost disappear at x = 0.08. Furthermore, Ba-substitution induces a weak and broad dielectric maximum in ε_b' vs. T curve at approximately T_m = 465 K for x > 0.2. Phase diagram of this system was proposed.

Keywords:

• Sr₂Nb₂O₇; Ba-substitution; single crystals; dielectric properties; phase diagram

Funding

This work was supported by JSPS KAKENHI Grant Number 25400329.