The heat capacities of fluorite-type Ba0.7La0.3F2.3 solid solution were studied by adiabatic (5-347 K) and drop (357-966 K) calorimetry. Experimental data, obtained in the present paper, as well as values of Ba0.7La0.3F2.3 thermodynamic functions, calculated for a wide temperature interval, can be used to estimate of energy of Gibbs of formation for modeling of phase diagram, determination of crystal growth conditions, and quantitative description of heterovalent isomorphism and features of laser optical materials. (C) 2013 Elsevier B.V. All rights reserved.