实用宽温区BCZT无铅电卡致冷叠层薄膜材料的研究

The depolarization electrocaloric effect in ferroelectric materials, which have broad application prospects in the electronic, information, energy and other fields, can allow the microelectronics and micro-electro-mechanical cooling system more miniaturization, high efficiency, low cost and environmental friendly. In this research, lead-free relaxor ferroelectrics with tetragonal, rhombohedra and cubic phase coexistence in Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BCZT) pseudo binary phase diagram will be investigated. Polycrystalline and single crystal thin film with high dielectric strength (> 500 kV/cm) and large maximum electrocaloric temperature change (ΔT > 20 K) will be prepared by the sol-gel method and the pulsed laser deposition (PLD) technique, respectively. Moreover, the multilayer ceramic capacitors (MLCC) technology is employed to design a laminated film structure with high cooling efficiency, supplying new environmental-friendly refrigeration materials and technical support for the younger generation of electronic devices. The doping of the La (A site) and (Ni1/3Nb2/3) (B site) would improved the degree of the dispersion around the phase transition temperature of BCZT relaxor ferroelectric thin films, as well as the shifting of the phase transition temperature near to room temperature and the broadening of the effective electrocaloric cooling zone (> 40 K), which is a novel procedure for seeking lead-free electrocaloric refrigeration materials with wide operation temperature.

利用铁电材料中退极化电卡致冷效应，可使得微电子与微机电制冷系统朝微型化、高效率、低成本与环保等趋势发展，在电子、信息、能源等领域具有广泛的应用前景。本研究将以无铅Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BCZT)伪二元相图中的四方、三方以及立方相共存点为研究体系，采用溶胶凝胶(sol-gel)与脉冲激光沉积(PLD)技术分别制备抗电场击穿强度高的(> 500kV/cm)、最大电卡致冷温度变化大的(ΔT > 20K)多晶与单晶薄膜，并借用多层陶瓷电容器(MLCC)技术设计出高效率致冷叠层膜结构，为下一代电子器件提供新的环保致冷材料与技术。通过La(A位)、(Ni1/3Nb2/3)(B位)等元素掺杂提高BCZT弛豫铁电薄膜相转变温度点处的弥散度，并使其相转变温度点移至室温附近，进而拓宽其有效电卡致冷温区(> 40K)，可望为实用型宽温区无铅电卡致冷材料提新思路。

利用铁电材料中退极化电卡致冷效应，可使得微电子与微机电制冷系统朝微型化、高效率、低成本与环保等趋势发展，在电子、信息、能源等领域具有广泛的应用前景。本项目采用溶胶凝胶法制备了一种La掺杂BCZT无铅弛豫铁电薄膜，该薄膜具有极高的电场击穿强度(> 3000kV/cm)、大的电卡致冷温度变化( > 20K)以及较宽的有效电卡制冷温区（> 40K）；制备了一种Bi(A位)、(Mg)(B位)元素共掺杂的BCT-BMT无铅类反铁电薄膜，该薄膜具有极低的漏电流，并展现出一个真实的负电卡制冷效应，该效应主要由外加电场下薄膜中特征拉曼振动模式半高宽的宽化所引起；研究了择优取向多相共存反铁电薄膜中的电卡制冷效应，结果表明薄膜制备过程中的面内残余拉伸热应力有利于大大增强其电卡制冷效应。研究成果可为新一代无铅固态电卡制冷材料及其器件的开发提供一定的实验和理论指导。