Phase Transition and Ferroelectric Characteristics of Pb[(Mg1/3Nb2/3)1-xTix]O3 Ceramics Modified with La(Mg2/3Nb1/3)O3

• Published in: Journal of the American Ceramic Society 1995-08, Vol.78 (8), p.2168-2174
• Main Authors: Wu, Tai-Bor, Shyu, Ming-Jyh, Chung, Chia-Chi, Lee, Hsin-Yi
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Ferroelectricity and antiferroelectricity; Phase transitions and curie point; Physics; Solid-solid transitions; Specific phase transitions
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.1995.tb08631.x

The effects of 0–5 mol% addition of La(Mg2/3Nb1/3)O3 (LMN) on the phase transition and ferroelectric behaviors of Pb[(Mg1/3Nb2/3)1‐xTix]O3 (PMNT) ceramics with compositions near the morphotropic phase boundary (MPB) were studied. An evolution of structure from rhombohedral to tetragonal was found with increasing PbTiO3 (PT) content across the MPB (at ∼32.5 mol% PT), and a coexistence of both rhombohedral and tetragonal phases was also found at the MPB. The dual‐phase field extended toward the lower PT content side of the MPB, and, moreover, the rhombohedrality or tetragonality was reduced, especially for the compositions near the MPB, by the addition of La in PMNT. The ferroelectric transition was found to change from normal to diffuse as the La content increased and the compositions became more rhombohedral. In accordance with the structural evolution, the change of remanent polarization (Pr) and coercive field (Ec) also became gradually indistinct, and both Pr and Ec were reduced. For compositions near the MPB, both PMNT and La‐modified PMNT had a similar electromechanical factor (kp) in a range around 0.55–0.60, but the mechanical quality factor (Qm) was significantly reduced for the La‐modified PMNT. The piezoelectric coefficient (d33), however, was largely improved with increasing La content in PMNT of compositions at MPB. A high value of d33∼ 815 pC/N was obtained for the 5‐mol%‐La‐modified ceramics, but it was associated with a low value of Qm.