Comparative Study of the Ferroelectric Specific Heat in TGS and DTGS

Abstract

A Comparative study has been made of the specific heat in single crystals of triglycine sulfate (TGS) and deuterated triglycine sulfate (DTGS). Measurements were performed (a) in the temperature interval 100-400 K, and (b) around the respective critical regions (at small temperature intervals ~0.02°C). In the low temperature region, both experimental curves were almost coincident, and they showed a temperature dependence indicative of strong anomalous anharmonicity. The heats of transition (ΔQ = 1.90± 0.10 joule/g.) and entropy change (ΔS=(6.21 ±0.30) joule/g°C) were almost the same for both crystals. The specific heat discontinuity was substantially different in both cases, ΔCP = 0.24± 0.03 joule/g°C for TGS, and ΔCP = 0.48± 0.03 joule/g°C for DTGS. Calculations based on both the thermodynamic theory and the statistical theory of ferroelectrics show fair agreement with the data. © 1975, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.