Studies of the heat capacity and dielectric properties of (1-x)BiFeO3-xPbFe0.5Nb0.5O3 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)PbFe0.5Nb0.5O3 with various x concentrations. It is shown that with an increase in the PbFe0.5Nb0.5O3 component, the temperatures of the ferroelectric and antiferromagnetic transitions in BiFeO3 shift to low temperatures. Taking into account structural studies, a "temperature-concentration" phase diagram has been constructed. Keywords: heat capacity, dielectric properties, ferromagnet, antiferromagnet, multiferroics.