Dielectric properties of various Ba(ZrxTi1-x)O3 ceramics under DC bias

Ba(ZrTi_1-x)O₃ (BZ_xT_1-x) ceramics with high Zr contents are electrostrictive materials with low M electrostriction constants. However, a multilayer ceramic capacitor (MLCC) with BZ_0.21T _0.79 composition exhibited a large strain of 0.6 μm at 0.1 kV/cm. Its apparent piezoelectric constant estimated, on the assumption that this MLCC is piezoelectrics, was 29,000 pm/V. This revealed that even if a piezoelectric constant of one layer is small, its multilayer ceramics can have ultrahigh piezoelectric constant. However, its strain vs. electric field behavior was not explained using an electrostrictive effect. Thus, dielectric properties of BZ_0.21T_0.79 ceramics under DC bias were investigated. As a result, the dielectric constants significantly decreased with increasing DC bias at room temperature. Thus, using a model considering DC bias dependence of dielectric constants, strain vs. electric field behavior of MLCC was explained. Temperature dependence of dielectric constants was also measured under DC bias. The dielectric peak shifted to higher temperature with increasing DC bias. The similar study was also done about BZ_xT_1-x ceramics with other composition