Specific heat anomalies and phase transitions in the solid solutions of PbHf1-xSnxO3

Abstract The heat capacity of antiferroelectric PbHf 1-x Sn x O 3 single crystals (0 < x < 0.35) was measured over a wide temperature range from 120 to 550 K using Differential Scanning Calorimetry. The temperatures and sequence of specific phase transitions were identified, and the resulting phase diagram was compared with dielectric and structural measurements. The total transition enthalpy and entropy at the phase transitions were calculated. Calorimetric studies of crystals with x < 0.07 revealed two sharp anomalies characteristic of first-order phase transitions, corresponding to transitions between the two antiferroelectric phases, AFE1 and AFE2, as well as between the AFE2 and paraelectric (PE) phases. These anomalies aligned well with the dielectric permittivity behaviour and structural data. Thermal hysteresis between heating and cooling cycles was also observed. Total latent heat (enthalpy) and entropy associated with the phase transitions were computed. The energy change and entropy variations indicate that the latent heat is primarily driven by structural transformations. As x increases, the latent heat of all phase transitions decreases. For x ≥ 0.07, a new phase transition was observed with negligible latent heat, confirming its second-order nature.