Heat capacity, thermal expansion and barocaloric effect in fluoride K2TaF7

摘要

The heat capacity and thermal expansion of potassium heptafluorotantalate were studied. The room temperature phase P2(1)/c is stable at least to 4 K. The strong first-order phase transition P2(1)/c Pnma at T0 1/4 486: 2K is accompanied by giant changes in the entropy, Delta S-0 = 22.3 J (mol K)(-1) and volume strain, delta V-0/V = -3: 6%. A rather high sensitivity of K2TaF7 to pressure was found, dT(0)/dp = -220KGPa(-1). Significant extensive and intensive barocaloric effects are found at low pressure. The possibility of improving the barocaloric properties is discussed.