Conditions Extrêmes et Matériaux : Haute Température et Irradiation
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2019

ACL
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M.Boča, Z.Netriová, A.Rakhmatullin, Z.Vaskova, E.Hadzimová, Ľ.Smrčok, O.Hanzel, B.Kubikova, 'The differing responses of various techniques in measuring the phase transformations of K2ZrF6', J. Mol. Liq. 287 110969 (2019) doi:10.1016/j.molliq.2019.110969

The compound K2ZrF6 undergoes an unusual multistep solid-solid transformation on temperature variation, whose irreversibility or reversibility depends on the target temperature: heating K2ZrF6 up to only 250 oC results in an irreversible process, while heating over this temperature results in reversible transformation. The reversibility of the back transformation indicates that α-K2ZrF6 transforms to a high-temperature phase (HTFrev) on heating above 250 oC, and on cooling reverts to the α-K2ZrF6 phase. The irreversible transformation involves transformation of α-K2ZrF6 to a hightemperature phase (HTFirrev) on heating to 250 oC, and then on cooling transforming to a mixture of meta-K2ZrF6 and K3ZrF7. With time this mixture changes to α-K2ZrF6, meta-K2ZrF6 and K3ZrF7. This transformation was monitored by DTA, DSC, 19F MAS NMR, XRD and thermal diffusivity techniques. Surprisingly, these experimental techniques showed unexpectedly differing responses.