Preparation of lead-free Sr2-xCaxNaNb5O15 (x = 0.1)-based piezoceramics with tungsten bronze structure

Abstract

This paper reported the development of lead-free Sr2-xCaxNaNb5O15 (SCNN, x = 0.1) piezoelectric ceramics with tungsten bronze structure that are potentially served as sensors in sensing patches. These ceramics were prepared using the conventional solid-state synthesis method, and their dielectric, ferroelectric and piezoelectric properties were investigated. The dual-stage sintering was used to densify SCNN ceramics, i.e. prefiring at 1240°C for 6 h and finally firing at 1280-1360°C for 25 h. The sample sintered at 1320°C exhibited the maximum density (4.96 g/cm3) and thus had the maximum dielectric constant (1455) and the Curie temperature (288°C). The spontaneous polarization and the piezoelectric constant of this sample were 7.9 μC/ cm2 and 118 pC/N, respectively. The electric properties of SCNN were improved by doping with 1 mass% La2O3, with the dielectric constant of 1662, the Curie temperature of 298°C, spontaneous polarization of 10.7 μC/cm2 and the piezoelectric constant of 138 pC/N, respectively. The good piezoelectric properties of the SCNN-based ceramics indicate that they are good candidates for sensor applications.