Bi-Based Lead-Free Piezoelectric Ceramics

Abstract

Dielectric, ferroelectric, and piezoelectric properties of Bi-based lead-free ferroelectric ceramics such as (Bi 1/2 Na 1/2 )TiO 3 [BNT], (Bi 1/2 K 1/2 )TiO 3 [BKT], and BiMeO 3 -based ceramics and their solid solutions are described in this chapter as one of the candidates for lead-free piezoelectric ceramics to reduce environmental damage. In Section 4.1 , the importance and necessity of environmentally friendly lead-free piezoelectric ceramics and a historical overview of lead-free development are described as an introduction. Section 4.2 shows physical and electrical properties of pure BNT ceramic. In particular, piezoelectric properties and depolarization temperature T d are the focus in order to understand fundamental behavior of physical properties including phase transition of pure BNT. BNT has rhombohedral symmetry ( R3c ) at room temperature, so solid solution systems with BKT and BaTiO 3 (BT) with tetragonal phases have a morphotropic phase boundary (MPB) between them. Dielectric, ferroelectric, and piezoelectric properties of BNT-BKT-BT system (near to MPB) combined with (Bi 1/2 Li 1/2 )TiO 3 (BLT) were summarized in Sections 4.3 and 4.4 . Also, doping effects of Mn ions to this system are discussed regarding their use in high-powered piezoelectric applications. Sections 4.5 and 4.6 include ferroelectric and piezoelectric properties of pure BKT and BKT-BT system, showing relatively good piezoelectric properties with wide working temperature ranges. Then, Section 4.7 provides a brief survey of ferroelectric properties of BiMeO 3 , indicating their distorted crystal structures and high potential of ferroelectricity.