Development of Reduction-Resistant Grain-Oriented BaTiO₃-Based Piezoelectric Ceramics

Abstract

Recently, development of lead-free piezoelectric materials has been receiving great attention because of environmental issues. Among several ferroelectric oxides, BaTiO₃ has been attractive as a potential candidate. In this study, we studied the processing of nonreducible BaTiO₃-based ceramics for multilayer piezoelectric actuator devices using base metal internal electrodes. Reduction-resistant BaTiO₃-based ceramics were fabricated by appropriately modifying the chemical composition in Mn-doped (Ba,Ca)TiO₃ ceramics. To improve their electrical properties, grain-oriented ceramics were also prepared by the reactive templated grain growth method using platelike BaTiO₃ and CaTiO₃ particles. The electrical properties of the BaTiO₃-based ceramics, sintered in the reducing atmosphere (oxygen partial pressure below 0.1 Pa), were markedly improved as a result of fabricating grain-oriented samples. Here, we have achieved an effective piezoelectric constant of approximately 570 pm/V and electrical properties (especially insulation resistance) which make it possible to apply to piezoelectric actuators.