Specific heat of tantalum carbides with various order parameters

Structural neutron diffraction method and adiabatic calorimetry were used to investigate low-temperature specific heat of tantalum carbide in 80-300 K range. To prepare samples with different order parameters two types of heat treatment conditions were used: quenching from 1900 K with 2000 deg/min cooling rate and long-term annealing at 1300 K. It is shown that tantalum carbide is characterized by higher specific heat in ordered (annealed) state, as compared to disordered one. Correlation with the values, calculated by computer, shows that experimental values of specific heat are lower, than corresponding theoretical ones. This is related with for order degree of particular sample, which is lower, than the maximal possible value