Changes in elastic compliance and piezoelectricity at ferroelastic phase transition in K₂ZnCl₄ crystals

Abstract

Temperature changes of normal and shear components of elastic compliance and piezoelectric tensors taking place in a low-temperature phase transition in K₂ZnCl₄ crystals were determined applying a series resonance method. On the basis of anomalous changes of the s₅₅ component of elastic compliance tensor and the d₁₅ component of piezoelectric tensor, it has been concluded that at the temperature T_ˆ = 145 K a ferroelastic phase transition occurs because of the change in symmetry: from the orthorhombic Pna2₁ to the monoclinic Alal with the spontaneous deformation η₅ as a secondary order parameter.