Influence of Grain-Growth Inhibitors on Modified (Ba,Sr)(Sn,Ti)O₃ for Electrocaloric Application

The paper reports on effect of grain-growth inhibitors MgO, Y₂O₃ and MnCO₃ as well as Ca modification on the microstructure, dielectric, ferroelectric and electrocaloric (EC) properties of Ba_0.82Sr_0.18Sn_0.065Ti_0.935O₃ (BSSnT). Furthermore, the effects of the sintering time and temperature on the microstructure and the electrical properties of the most promising material system Ba_0.62Ca_0.20Sr_0.18Sn_0.065Ti_0.935O₃ (BCSSnT-20) are investigated. Additions of MgO (x_MgO = 1%), Y₂O₃ (x_Y = 0.25%) and MnCO₃ (x_MnCO = 1%) significantly decreased the mean grain size of BSSnT to 0.4 µm, 0.8 µm and 0.4 µm, respectively. Ba_0.62Ca_0.20Sr_0.18Sn_0.065Ti_0.935O₃ (BCSSnT-20) gained a homogeneous fine-grained microstructure with an average grain size of 1.5 µm, leading to a maximum electrocaloric temperature change |ΔT_EC| of 0.49 K at 40 °C with a broad peak of |ΔT_EC| > 0.33 K in the temperature range from 10 °C to 75 °C under an electric field change of 5 V µm^-1. By increasing the sintering temperature of BCSSnT-20 from 1350 °C to 1425 °C, the grain size increased from 1.5 µm to 7.3 µm and the maximum electrocaloric temperature change |ΔT_EC| increased from 0.15 K at 35 °C to 0.37 K at 20 °C under an electric field change of 2 V µm^-1. Our results show that under all investigated material systems, BCSSnT-20 is the most promising candidate for future application in multilayer ceramic (MLC) components for EC cooling devices.