Dielectric Properties and Phase Diagram of (Sr1-xBax)2Nb2O7 Single Crystals

Abstract

Dielectric constants, εb′ and εc′ 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 TI = 489 K and at TL = 100 K, owing to the incommensurate phase transition and the low-temperature ferroelectric phase transition, respectively. Both TI and TL 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 εb' vs. T curve at approximately Tm = 465 K for x > 0.2. Phase diagram of this system was proposed.