Growth and Di-/Piezoelectric Properties of Al-Doped PMN-30PT Single Crystals

Aluminum (Al3+)-doped Pb(Mg1/3Nb2/3)O-3-30PbTiO(3) (PMN-30PT) solid solution piezo-crystals were grown by a top-seeded solution growth method. The dielectric, piezo-, and ferro-electric properties were characterized. A dispersive maximum of dielectric permittivity was found around T-c = 135 degrees C, which does not depend on frequency. Interestingly, the rhombohedral-tetragonal phase transition, which appears at 60 degrees C in pure PMN-PT and thereby causes the depoling of the crystals at a relatively low temperature, has been increased to 105 degrees C by means of the Al3+-doping. This extends the upper limit of application temperature for electromechanical transducers up to the T-c. The piezoelectric coefficient (d(33)) was found to be 2000 pC/N at room temperature. The longitudinal electromechanical coupling factor k(33) reaches 85-90%, which shows a good thermal stability upon heating up to 135 degrees C. The peak to peak bipolar strain was measured to be 0.25% at an electric field of up to 17 kV/cm.