Thermodynamics of the lanthanide trifluorides. IV. The heat capacities of gadolinium trifluoride GdF3, lutetium trifluoride LuF3, and yttrium trifluoride YF3 from 5 to 3500K

The heat capacities of three isostructural trifluorides GdF3, LuF3, and YF3 were determined from 5 to 3500K by adiabatic calorimetry. Below 150K GdF3 contained an excess heat capacity contribution over the usual lattice heat capacity; LuF3 and YF3 showed no unusual heat capacities over the entire temperature range. Results in tabular form which list the heat capacity C0/sub p/, the entropy S0, the enthalpy [H0(T)-H0(0)], and the Planck function -[G0(T)-H0(T)]/T are given for the three trifluorides. Also presented are recommended thermochemical functions at 298.150K and tables of recommended high-temperature thermodynamic functions from 4000K to the melting temperatures. The excess entropy associated with GdF3 is discussed and values of the lattice heat capacity of GdF3 below 150K are estimated