Calorimetric analysis of NaF and NaLaF4

Heat flux calorimetry was used to measure the heat capacity of NaF between 630 K and 1100 K. The results agreed well with previous measurements known from the literature. Similar experiments were performed on NaLaF4. This compound was synthesized from NaF and LaF3 and analyzed by X-ray diffraction. The heat capacity of NaLaF4 was determined for two temperature ranges: from 4 K to 400 K, for which adiabatic calorimetry, and from 623 K to 1213 K for which differential scanning heat flux calorimetry was used. The two heat capacity series fit smoothly; the resulting Cp,m function was used in a reassessment of the binary system (NaF + LaF3).