Elastic stability of high coupling ternary single crystals

A sub-hertz harmonic force was used to investigate the elastic response of ternary (1-y-x)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT) single crystal with compositions (x = 0.30 and x = 0.33) near the Morphotropic Phase Boundary (MPB) under isothermal and zero-field conditions. The observed instability under mechanical compression is attributable to a ferroelectric rhombohedral FR-ferroelectric orthorhombic FO phase transformation. The associated strain is a function of proximity to MPB and is consistent with the prediction of the classical Devonshire theory. Isothermal resonance-antiresonance frequency sweeps versus temperature revealed a non-vertical MPB with (∂TRT/∂x)<0, where TRT is the rhombohedral-tetragonal transition temperature. These results provide insights into the role of PT content on the stability of PIN-PMN-PT crystals used for electromechanical devices and sound projectors.