High intensity focused ultrasound (HIFU) and ultra sound-guided HIFU therapy require probes capable of both high quality diagnostic imaging and radiating high acoustic power into tissue. Piezoelectric materials with high mechanical quality factor Q, large electromechanical coupling (kij) and high dielectric constant KT are desired to meet the demands of advanced high power electromechanical applications. In addition, a high Curie temperature is desired because of wider temperature usage and improved temperature stability. Previous investigations have shown that Q or k ij and KT can be enhanced only at the expense of each other. Also materials with higher Curie temperature were found to possess lower dielectric and piezoelectric performance. Therefore, modified piezoelectric materials (including polycrystalline and single crystals) were reviewed as a function of Curie temperature. Optimization of performance was exemplified with Pb(Sc1 / 2Nb1 / 2)O3-PbTiO3 (PSNT) compositions close to the morphotropic phase boundary (MPB) and the effect of manganese additions on Q, coupling k33 and KT, respectively. �� 2005 Elsevier B.V. All rights reserved.