Large electromechanical strain at high temperatures of novel textured BiFeGaO3-BaTiO3 based ceramics

Abstract

BiFeGaO3-BaTiO3 (BFG-BT) based ceramics with a large piezoelectric coefficient are potential high performance lead-free piezoelectric compounds. In this work, textured and random BFG-BT ceramics were realized by the solid state reaction method with and without BaTiO3 (BT) templates. Textured ceramics were obtained by a reactive templated grain growth (RTGG) method leading to a high-temperature electromechanical strain of S = 0.27 % at 40 kV/cm and to an effective piezoelectric coefficient (d33*) up to 685 pm/V at 180 °C. The easy movement of oriented domains enhanced the electromechanical strain under an applied electric field in textured sample (Lotgering factor f = 66.3 %). Structural investigations reveal that the proportion and degree of distortion of BFG-BT rhombohedral phase (R3c) reached its maximum in textured ceramics, resulting in large ferrodistortive displacements under electric fields. In addition, the dense nanodomains with low domain wall energies, inferred from the high-resolution transmission electron microscope (HR-TEM) observations, contribute to the extra displacement of the textured sample under an applied electric field. In textured ceramics, the remnant polarization was stable (about 17 μC/cm2) from room temperature to 180 °C, contributing to the stable ferroelectric property at high temperatures. Through the introduction of BT templates, high-density nanodomains were formed and the Burns temperature was enhanced in textured ceramics. The electromechanical strain, polarization and dielectric behavior were correlated to the textured or random forms of the BFG-BT based ceramics.