Effect of Sn Addition on Thermodynamic, Dielectric, Optical, and Acoustic Properties of Lead Hafnate

Abstract

Specific heat, dielectric properties, domain structure, and Brillouin light scattering studies in antiferroelectric PbHf1−xSnxO3 single crystals with three different concentrations (x = 0.08, 0.1, and 0.23) are performed in function of temperature. The specific heat and dielectric data reveal clear anomalies at three temperatures denoted as T1, T2, and TC. At T1, transition from the antiferroelectric AFE1 to another antiferroelectric AFE2 phase is realized, the next phase transition (PT) is from AFE2 to an intermediate (IM) phase—at T2, and from IM to paraelectric (PE) phase at TC. PTs at T1 and T2 are definitely of the first order, whereas the PT at TC has features of the second‐order PT. The PT sequences are confirmed by changes in the domain structure. In the PE phase, Brillouin studies reveal the softening and broadening of longitudinal acoustic (LA) mode in the cooling process. The softening and broadening exhibit the maximum values near TC. The transverse acoustic (TA) mode appears near T2. Additional acoustic anomalies are also observed at T1. The temperature dependencies of LA mode indicate the existence of polar regions in PE phase and order–disorder character of the PT at TC. The other PTs are mainly of a displacive character.