Abstract
Effects of hydrostatic pressure on the phase transitions in ferroelectric Ca 2 Sr(C 2 H 5 COO) 6 and Ca 2 Pb(C 2 H 5 COO) 6 were studied by dielectric constant measurements in a temperature range of -100∼ +200°C and a pressure range up to about 8.5 kbar. The I-II transition temperatures (8.7°C in the Sr-salt, 60.4°C in the Pb-salt at 1 atm) monotonically increase with increasing pressure with initial slopes of 19.7 deg kbar -1 for the Sr-salt and 23.4 deg kbar -1 for the Pb-salt, respectively. The II-III transition temperatures (-173°C in the Sr-salt, -88°C in the Pb-salt at 1 atm) increase with increasing pressure, and the first order II-III phase boundaries terminate at critical points of p crit =3.35 kbar; T crit =-35°C in the Sr-salt, and p crit =1.73 kbar; T crit =-41°C in the Pb-salt, respectively. A sharp maximum of low frequency dielectric constant was found at the critical point of the Pb-salt.
Published Version
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