Influence of Grain-Growth Inhibitors on Modified O[sub.3] for Electrocaloric Application

The paper reports on effect of grain-growth inhibitors MgO, Y[sub.2]O[sub.3] and MnCO[sub.3] as well as Ca modification on the microstructure, dielectric, ferroelectric and electrocaloric (EC) properties of Ba[sub.0.82]Sr[sub.0.18]Sn[sub.0.065]Ti[sub.0.935]O[sub.3] (BSSnT). Furthermore, the effects of the sintering time and temperature on the microstructure and the electrical properties of the most promising material system Ba[sub.0.62]Ca[sub.0.20]Sr[sub.0.18]Sn[sub.0.065]Ti[sub.0.935]O[sub.3] (BCSSnT-20) are investigated. Additions of MgO (x[sub.MgO] = 1%), Y[sub.2]O[sub.3] (x[sub.Y2O3] = 0.25%) and MnCO[sub.3] (x[sub.MnCO3] = 1%) significantly decreased the mean grain size of BSSnT to 0.4 µm, 0.8 µm and 0.4 µm, respectively. Ba[sub.0.62]Ca[sub.0.20]Sr[sub.0.18]Sn[sub.0.065]Ti[sub.0.935]O[sub.3] (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[sub.EC]| of 0.49 K at 40 °C with a broad peak of |ΔT[sub.EC]| > 0.33 K in the temperature range from 10 °C to 75 °C under an electric field change of 5 V µm[sup.−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[sub.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[sup.−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.