Intrinsic ferroelastic transition from a piezoelectric paraelastic phase

Abstract

“Intrinsic (proper) ferroelastic transition” is defined as the transition of which the primary order parameter is the homogeneous strain. When a given crystal happens to have piezoelectric couplings in the paraelastic phase, the condition that should be satisfied in order for the crystal to be an intrinsic ferroelastic crystal is proposed on the basis of the Landau theory.The LiNH4C4H4O6·H2O (abbreviated as LAT) crystal does in fact satisfy the above condition, and thus, is called an intrinsic ferroelastics. The 2,2,6,6-Tetramethyl Piperidino Oxy (Tanane) crystal satisfies also the above condition, thus presumably is an intrinsic ferroelastic crystal.The above idea is extended to all the cases where piezoelectric couplings exist in the paraelastic phase, and therefore the ferroelastic phase is simultaneously ferroelectric.