The temperature dependence of the heat capacity of the multiferroics BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 has been studied. It was found that the substitution of europium and samarium ions for bismuth ions in bismuth ferrite leads to the appearance of an additional heat capacity component due to transitions of 4f - electrons of rare earth ions to higher levels of the multiplet. A connection is established between the decrease in phonon thermal conductivity and the Schottky effect for the specific heat.

The heat capacity and dielectric properties of microcrystalline and nanostructured SmFeO_3 ceramics obtained by solid phase synthesis are studied. The ceramics is synthesized by the treatment of the batch at room temperature in Bridgman anvils by forceful action combined with shear deformation followed by sintering. It is established that the mechanoactivation results in noticeable broadening antiferromagnetic–ferroelectric transition and shifting the temperature of phase transition in the low-temperature area. The phase transition having typical for relaxation oscillator frequency dependent character is found at 558 K. It is shown that the defect structure can take a dominant place in the formation of the physical properties of ceramics.

The temperature dependence of the heat capacity of nanostructured SmFeO3 ceramics obtained by mechanical activation in the temperature range of 120–800 K has been studied. It has been shown that the excess heat capacity of mechanically activated ceramics is due to: displacements of iron and samarium ions and with a change in the angle between FeO6 oxygen octahedra.

The temperature dependence of the heat capacity of the CoFe2O4 ferromagnet and the 0.3CoFe2O4–0.7PbTiO3 multiferroic composite in the temperature range 150–820 K has been studied. heat capacity over a wide temperature range. It is noted that the additional component of the heat capacity is due to the transition of cobalt or iron ions to higher energy levels, as well as due to the distortion of the lattice parameters due to the appearance of three coexisting phases.

The thermophysical properties of the ferroelectric PbFe0.5Nb0.5O3 in the temperature range 300–800 K are studied. Anomalies in the heat capacity and thermal diffusion are found in the region of the diffuse ferroelectric transition Tc~380 K, the Burns temperature Td~670 K, and the intermediate temperature T^*~470 K. The dominant phonon heat transfer mechanisms in a ferroelectric with a nanopolar structure.