Heat capacity, thermal expansion and barocaloric effect in fluoride K2TaF7

Flerov, I. N.; Gorev, M. V.; Kartashev, A. V.; Pogorel'tsev, E. I.; Laptash, N. M. Source: JOURNAL OF MATERIALS SCIENCE, 54 (23):14287-14295; 10.1007/s10853-019-03924-8 DEC 2019

The heat capacity and thermal expansion of potassium heptafluorotantalate were studied. The room temperature phase P21/c is stable at least to 4 K. The strong first-order phase transition P21/cPnma at T0=486.2K is accompanied by giant changes in the entropy, ΔS0=22.3J(molK)1, and volume strain, δV0/V=3.6%. A rather high sensitivity of K2TaF7 to pressure was found, dT0/dp=220KGPa1. Significant extensive and intensive barocaloric effects are found at low pressure. The possibility of improving the barocaloric properties is discussed.