摘要 : The para-ferroelectric tricritical phase transition of a single crystal of triglycine selenate (TGSe) has been studied in the neighbourhood of the transition temperature, under weak electric fields, E, using a highly sensitive cal... 展开 The para-ferroelectric tricritical phase transition of a single crystal of triglycine selenate (TGSe) has been studied in the neighbourhood of the transition temperature, under weak electric fields, E, using a highly sensitive calorimetric technique. The specific heat, c(E), under fields in the range between 5 and 175 V cm(-1) and close to transition temperature (0.2 K), shows different behaviour on cooling and on heating at a temperature variation rate of +/- 0.03 K h(-1); for T < T-c -0.5 K all sets of data match each other. The experimental data have been fitted to the 2-6 Landau potential obtained for E = 0; a term -xi Q, taking into account the coupling between E (xi being dependent on E) and the order parameter Q, is included. This potential fits well with the experimental data in the ferroelectric phase. The different relation between xi and E obtained on heating and on cooling runs is discussed and it is concluded that data on heating correspond to the thermal equilibrium. 收起