Piezoelectric instability in 〈011〉-oriented Pb(B1/3IB2/3II)O3–PbTiO3 crystals

Piezoelectric investigations of 〈011〉-oriented Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) and Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZN–PT) crystals have revealed high electromechanical properties. Piezoelectric constants of up to 5000–6000 pC/N and electromechanical coupling coefficients of up to 0.95 have been observed near the ferroelectric rhombohedral to ferroelectric tetragonal transformation. The data clearly demonstrate that the enhanced electromechanical performance of oriented piezocrystals is not constrained to the 〈001〉 orientation. Furthermore, analysis of the data has demonstrated the presence of piezoelectric instability between two ferroelectric states at a critical transformation temperature and/or electric field.