Thermodynamic properties and phase transitions of multiferroics (1-x)BiFeO$_{3-x}$PbFe$_{0.5}$Nb$_{0.5}$O$_3$

Studies of the heat capacity and dielectric properties of (1-x)BiFeO$_{3-x}$PbFe$_{0.5}$Nb$_{0.5}$O$_3$ ceramic multiferroics in the temperature range of 300–800 K were carried out. Based on studies of the temperature and concentration dependences of the heat capacity and dielectric constant, the phase transition temperatures of the (1-x)BiFeO3 system were determined. (1-x)BiFeO$_{3-x}$PbFe$_{0.5}$Nb$_{0.5}$O$_3$ with various x concentrations. It is shown that with an increase in the PbFe$_{0.5}$Nb$_{0.5}$O$_3$ component, the temperatures of the ferroelectric and antiferromagnetic transitions in BiFeO$_3$ shift to low temperatures. Taking into account structural studies, a “temperature-concentration” phase diagram has been constructed.