Abstract
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 \(T_0=486.2\,\hbox {K}\) is accompanied by giant changes in the entropy, \(\Delta S_0=22.3\,\hbox {J}\,(\hbox {mol}\,\hbox {K})^{-1},\) and volume strain, \(\delta V_0/V=-\,3.6\%\). A rather high sensitivity of \(\hbox {K}_{2}\hbox {TaF}_{7}\) to pressure was found, \({\text {d}}T_0/{\text {d}}p=-\,220 \,\hbox {K}\,\hbox {G}\,\hbox {Pa}^{-1}\). Significant extensive and intensive barocaloric effects are found at low pressure. The possibility of improving the barocaloric properties is discussed.
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The reported study was funded by RFBR according to the research Project No. 18-02-00269_a.
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Flerov, I.N., Gorev, M.V., Kartashev, A.V. et al. Heat capacity, thermal expansion and barocaloric effect in fluoride \(\hbox {K}_{2}\hbox {TaF}_{7}\). J Mater Sci 54, 14287–14295 (2019). https://doi.org/10.1007/s10853-019-03924-8
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DOI: https://doi.org/10.1007/s10853-019-03924-8