Heat capacities and thermodynamic functions of new nanosized ferro-chromo-manganites LaM0.5IIFeCrMnO6.5 (MII–Mg, Ca, Sr, Ba)

Resumo

The heat capacities of nanosized ferro-chromo-manganites LaM_0.5^IIFeCrMnO_6.5 (M^II–Mg, Ca, Sr, Ba) are measured via dynamic calorimetry in the temperature range of 298.15–673 K using an IT-S-400 instrument. It is established that the C°_p~f(T) function of LaM_0.5^IIFeCrMnO_6.5 (M^II–Mg, Ca, Sr, Ba) has λ-type effects, due probably to phase transitions of the second order. Considering the temperatures of the phase transitions, equations of the heat capacity of ferro-chromo-manganites LaM_0.5^IIFeCrMnO_6.5 (M^II–Mg, Ca, Sr, Ba) as a function of temperature are derived on the basis of experimental data. Thermodynamic functions Н°(Т)–Н°(298.15), S°(Т), and Ф^хх(Т) are calculated in the temperature range of 298.15–675 K.