We use molecular dynamics simulations for a first principles-based effective Hamiltonian to calculate two important quantities characterizing the electrocaloric effect in BaTiO$_3$, the adiabatic temperature change $ΔT$ and the isothermal entropy change $ΔS$, for different electric field strengths. We compare direct and indirect methods to obtain $ΔT$ and $ΔS$, and we confirm that both methods indeed lead to identical result provided that the system does not actually undergo a first order phase transition. We also show that a large electrocaloric response is obtained for electric fields beyond the critical field strength for the first order phase transition. Furthermore, our work fills several gaps regarding the application of the first principles-based effective Hamiltonian approach, which represents a very attractive and powerful method for the quantitative prediction of electrocaloric properties. In particular, we discuss the importance of maintaining thermal equilibrium during the field ramping when calculating $ΔT$ using the direct method within a molecular dynamics approach.
Quasi-indirect measurement of electrocaloric temperature change in PbSc0.5Ta0.5O3 via comparison of adiabatic and isothermal electrical polarization data
Electrocaloric effect in Ba(0.2)Ca(0.8)Ti(0.95)Ge(0.05)O(3) determined by a new pyroelectric method
本文研究了无铅氧化物Ba_（0.8）Ca_（0.2）Ti_（0.95）Ge_（0.05）O_3陶瓷（BCTG）的电热效应。利用Maxwell关系式（dT/dE）~（dP/dT）_E，用两种不同的方法测定了电热响应率（dT/dE）。在第一种众所周知的间接方法中，在宽的温度范围内测量P-E滞后回线，从该温度范围通过P（T，E）数据的推导确定热释电系数p_E=（dP/dT）_E和（dT/dE）。在第二种新方法中，热释电系数p_E和电热响应度是通过直接测量不同外加电场下的热释电电流来确定的。在实验误差范围内，两种方法之间的一致性很好，电热响应率等于0.18 +/- 0.05 × 10-6 K. m. V-1，在410 K左右获得
Electrocaloric effect and high energy storage efficiency in lead-free Ba$_{0.95}$Ca$_{0.05}$Ti$_{0.89}$Sn$_{0.11}$O$_3$ ceramic elaborated by sol-gel method
研究了溶胶-凝胶法制备的无铅陶瓷Ba $_{0.95}$ Ca $_{0.05}$ Ti $_{0.89}$ Sn $_{0.11}$ O $_3$（BCTSn）的结构、介电、铁电、储能和电热效应。使用Rietveld精修分析从X射线数据确认相纯度结构，其揭示了在室温下四方晶系（P4 mm）和正交晶系（Amm 2）对称性的共存。相变检测介电和差示扫描量热法的结果。储能性能由P-E滞后确定，电热性能通过Maxwell方法间接计算。在30 kV cm $^{-1}$的相对小的电场下获得的$Δ$ T=0.807 K的大的电热温度变化值和高的能量存储效率可以使BCTSn陶瓷成为环境友好的制冷和能量存储应用的有希望的候选者。
The Influence of Chemical Strains on the Electrocaloric Response, Polarization Morphology, Tetragonality and Negative Capacitance Effect of Ferroelectric Core-Shell Nanorods and Nanowires
Electrocaloric effects in the lead-free Ba(Zr,Ti)O$_{3}$ relaxor ferroelectric from atomistic simulations
采用原子有效哈密顿方法研究了Ba（Zr $_{0.5}$ Ti $_{0.5}$）O $_{3}$（BZT）弛豫铁电体的电热效应.我们发现，EC系数在任何温度下随电场非单调变化，呈现出最大值，可以追溯到BZT的极性纳米区域的行为。我们还介绍了一个简单的朗道为基础的模型，再现的EC行为的BZT作为场和温度的函数，这是直接适用于其他化合物。最后，我们确认，对于低温（即，在非遍历条件下），测量EC响应的通常间接方法提供了与场诱导温度变化的直接评估定量不同的估计。
Enhanced electrocaloric and energy-storage properties of environment-friendly ferroelectric Ba0.9Sr0.1Ti1-xSnxO3 ceramics
研究了采用传统固相反应法制备的环境友好型Ba 0. 9 Sr 0. 1 Ti 1-xSnxO 3（BSTS-x）铁电陶瓷的电热效应和储能性能。在我们的样品中发现了超过80%的显著能源效率。特别地，BSTS-5和BSTS-10样品在室温（RT）附近的宽温度范围内分别表现出92%和88%的效率。直接EC测量和间接方法的基础上的热力学方法被用来表征EC效应，两者都得到了一致的结果。BSTS-0在368 K下获得了最大的电热响应率0.73 K mm/kV，在仅为7.4 kV/cm的低外加电场下绝热温度变化DT（EC）为0.55 K。随着Sn含量的增加，BSTS-x陶瓷的EC响应降低，而它们的扩散性在以RT为中心的广泛的温度范围内增加。研究结果表明，设计具有更高EC效应和能量效率的环境友好型材料用于潜在的固态制冷和储能装置是可能的。
