The electrocaloric effect of Ba_(1-x)La_xTi_(0.9)Sn_(0.1)O_3 ceramics with excellent temperature stability near room temperature

摘要

The Ba_(1-x)La_xTi_(0.9)Sn_(0.1)O_3 ceramics (x = 0, 0.006, 0.007, 0.008) were prepared by the traditional solid-state reaction method. The infuence of La~(3+) on the phase, dielectric properties, ferroelectric properties, and electro-caloric effect (ECE) was analyzed in detail. The results of refnement show that all ceramics are multiphase coexistence at room temperature, including the cubic phase, the tetragonal phase, and the orthogonal phase. With the increase of La~(3+), the polar phases decrease but the non-polar phase increases, which is the main reason for the decline in adiabatic temperature change (ΔT). The analysis of dielectric properties and ferroelectric properties demonstrate that the diffuse phase transition is strengthened by introducing La~(3+). It also means that polar nanoregions (PNRs) might be formed. Therefore, the temperature stability of the Ba_(1-x)La_xTi_(0.9)Sn_(0.1)O_3 ceramics in a wide temperature range near room temperature is improved. Simultaneously, the PNRs provide additional entropy to improve ECE. A higher ΔT = 0.88 K is obtained under 60 kV/cm for x = 0.007, which also possesses excellent temperature stability in the temperature range of 298 K-378 K. The doping of La~(3+) also improves the electric feld threshold of the electrocaloric strength (ΔT_(max)/ΔE) and stabilizes the ΔT_(max)/ΔE under a higher electric feld, which is conducive to improving ECE under a higher electric feld and providing another possible solution for promoting the practical application of ECE.