Effect of Different Nano-oxide Addition on Densification, Microstructure, Electrical and Mechanical Properties of Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BZT–BCT) Ferroelectric Ceramics

Abstract

Piezoelectric ceramics are widely used as actuator, resonator, and spark igniter. Recently, much attention has been paid to prepare BZT-BCT piezoelectric ceramics because of its good dielectric, piezoelectric properties and environment friendly nature. However, piezoelectric ceramics based on BaTiO3 suffer from low reliability and poor mechanical properties such as strength and toughness. A novel method has been used to improve the mechanical properties of ceramics by reinforcement of matrix with stronger oxide (Al2O3, MgO, ZrO2, Stabilized-ZrO2) or nonoxide (SiC) particles. It is well known that electrical properties of ferroelectric ceramics generally degrade with non-ferrolecric additives and decrease in sinterability usually encountered with these refractory oxide additives. Use of nano-oxide additives may drastically reduce the amount of additive and in effect electrical property may not degrade much.
The aim of this work is to study the densification, microstructure, electrical and mechanical properties of BZT–BCT with nano oxide additives (Al2O3, MgO, and stabilized-ZrO2). BZT-BCT powders were prepared successfully by a conventional mixed-oxide method via planetary-milling technique. BZT–BCT composites were prepared by mixing high purity BZT–BCT powder and small amount (0.5-2.0 vol%) of oxides, i.e. Al2O3, MgO and ZrO2(3Y) separately. The flexural strength and hardness of BZT–BCT composites were increased significantly for all the three nano-oxide addition. It was found that nano-oxides addition improves densification and significantly modifies the microstructure. Though the relative permittivity and piezoelectric constant of the composites were decreased with the addition of nano-oxide, the decrement was sharp for MgO whereas it was least for Al2O3. Change in grain size, distribution of oxide particle and formation of secondary phases were used to explain the properties. 1 vol% Al2O3 added BZT-BCT will be useful for devices like low power transducers, where extremely high dielectric constant and high "d" constant required.