Thermal and elastic properties of ferroelastic (NH4)4LIH3(SO)4

Abstract Results of DTA, thermal expansion and elastic properties studies of (NH4)4LiH3(SO)4 single crystal in the temperature range covering its ferroelastic phase transition are reported. It is concluded that the 4 → 2 transition observed at about 232 K is a second order proper one with the spontaneous strain as the primary order parameter.