Large electrostrictive coefficients of BaTiO<sub>3</sub>-based lead-free ceramics

Abstract

AbstractMicro-displacement actuators have important applications in aerospace, semiconductor, industry and other fields. Now most of the lead-based piezoelectric ceramics are used in the market. In consideration of environmental protection and legal restriction, it is urgent to develop lead-free ceramic materials with excellent electrostrictive properties. As a kind of ABO<sub>3</sub>-type ferroelectrics, (Ba,Ca)(Ti,Zr)O<sub>3</sub> lead-free ceramics have attracted a lot of attention because of their high piezoelectricity. In this work, (Ba<sub>0.85</sub>Ca<sub>0.15</sub>)(Ti<sub>0.9</sub>Zr<sub>0.1</sub>)O<sub>3</sub> (BCTZ) ceramics with high electrostrictive coefficient are prepared by the solid-state method. The effects of sintering temperature on the structures and electrical properties of BCTZ ceramics are studied. The results show that the sintering temperature can help to improve density and grain growth of BCTZ ceramic.There are no impurity phases in the BCTZ ceramic systems, and all samples show ABO<sub>3</sub>-type perovskite structures. At room temperature, the crystal structure of BCTZ ceramic forms coexistence of orthogonal (O)-tetragonal (T) phase. The dielectric peak of BCTZ ceramic is widened, and the Curie temperature reaches a maximum value of 110 ℃ when <i>T</i><sub>s</sub> = 1300 ℃. With the increase of sintering temperature, the dielectric peak of BCTZ ceramic gradually becomes narrowed, and the Curie temperature of ceramic moves toward low temperature.As the sintering temperature is 1300 ℃, the grain size of BCTZ ceramic is 1 μm, the large electrostrictive coefficient <i>Q</i><sub>33</sub> (5.84 × 10<sup>–2</sup> m<sup>4</sup>/C<sup>2</sup>) can be obtained, which is about twice that of traditional PZT ceramic. This may be attributed to combination of the surface effect caused by grain size of BCTZ ceramic with the strong ionic nature of A-O chemical bond. In addition, although BCTZ ceramic has an O-T phase boundary near room temperature, the electrostrictive coefficient <i>Q</i><sub>33</sub> of ceramic has good temperature stability in a range of 25–100 ℃. It shows that the crystal phase and temperature have no effect on the electrostrictive coefficient of BCTZ lead-free ceramic. It provides a new idea for designing the high electrostrictive properties of lead-free piezoelectric ceramics with potential applications.