Dielectric Study of the Phase Transitions of Ca₂Ba(C₃H₇COO)₆ (DBB)

Abstract

Phase transitions in dicalcium barium butyrate, Ca₂Ba(C₃H₇COO)₆ (DBB), have been studied by dielectric measurements. At atmospheric pressure, two first order phase transitions are detected at 325 K (I–II transition) and 212 K (II–III transition). A dielectric relaxation with the activation energy of about 0.21 eV is observed in the lowest-temperature III phase. Effect of hydrostatic pressure on the phase transitions was measured and the pressure–temperature (p–T) phase diagram was obtained. The initial pressure coefficients of the I–II and II–II transition temperatures are 0.50 K/MPa and 0.08 K/MPa, respectively. Two pressure-induced phases, IV and V, were found. Unlike to the corresponding propionate crystal Ca₂Ba(C₂H₅COO)₆ (DBP) none of the pressure-induced phases show ferroelectric activity.