基于电卡效应的原型致冷器基础研究

The electrocaloric effect is the change in entropy of a dielectric material due to the electric-eld induced change in the degree of ordered state, accompanied with the temperature change of material due to the releasing or absorbing of heat. That is to say, with the applied electric-field, the entropy will increase due to the increasing of degree of ordered state, accompanied with the increasing of temperature due to the releasing of heat. Removing the applied electric-field, the entropy will decrease due to the decreasing of degree of ordered state, accompanied with the decreasing of temperature due to the absorbing of heat. Based on the new physical effect, ferroelectric refrigeration or solid-state refrigeration will be developed for the new cooling technology, which is more efcient and environmentally friendly compared to the conventional vapor compression cycle approach, and have the great promise for cooling, such as the heat dissipation of CPU. In this research, we focus the fundamental research of cooling device based electrocaloric effect. The electrocaloric effect of PZT based ferrolectric and antiferroelectric materials will be systematically investigated firstly, and different factors on improving electrocaloric effect will be considered and optimized. The composition with the large ECE will be obtained at room temperature. In order to increasing the breakdown field strength and heat capacity, the fabrication of samples with thick film and multi-layer technology will be developed for cooling device. Based on the multi-functional effects, including the electrocaloric and inverse piezoelectric effects, a prototype device with carnot cycle for cooling will be designed, developed and evaluated. The optimization of composition, preparation of sample with multi-layer and design of device with carnot cycle will be involved in the research of cooling prototype device based on electrocaloric effect, and the key technology will be revealed.

电卡效应指的是电介质材料在电场作用下，其材料内部有序度变化所导致的熵变，以及相应的吸放热在材料温度上的反映，即电介质材料在绝热条件下，加电场极化、有序度增加、熵减少，放热和升温；而去电场退极化、有序度减小、熵增加，吸热和降温。基于这种新物理效应可发展新的致冷技术及器件-铁电致冷器(固态致冷器)，在解决微电子产品的致冷需求，如CPU散热等领域具有广泛应用前景。本项目拟在此方面开展基础研究，通过对PZT基铁电-反铁电材料电卡效应的研究，分析电场诱导下的结构相变及各种因素对电卡效应的影响，获得室温时具有实际应用价值的材料组份；采用厚膜叠层工艺制备多层结构样品，增大材料的击穿场强和热容量；利用铁电材料的多功能性，特别是电致应变，通过结构设计研究可形成卡诺循环的微型制冷器原型器件，并对致冷效果进行评价和优化。项目围绕着电卡效应机理、材料组分优化、厚膜多层试样、原型致冷器件设计等关键技术开展基础研究。

本课题首先围绕着不同铁电材料体系的组份、制备、工艺和性能之间的相互关系开展研究，进而实现电卡效应的调控和优化，同时开展了基于电卡效应原型器件的基础研究，取得了以下几方面成果：对不同铁电体材料的组份和结构性能的关系进行了详细研究，包括不同制备工艺和条件、掺杂、温度、电场等条件的变化对铁电-反铁电结构和性能、场诱相变临界参数、介电和极化强度响应的影响。通过对不同铁电材料体系性能的详细研究和细致分析，获得了大量有价值的实验数据和结果；在铁电陶瓷多层同质膜和异质膜方面开展了制备研究和性能测试。基于电卡效应原型致冷器件的设计思路，模拟和优化研究，对比不同的热量输运模式，提出了不同的器件设计构思，同时开展了基于压电效应和电卡效应相互融合的模拟分析，认为通过压电效应驱动来输运热量，是可以实现致冷的，即冷端温度不断降低、热端温度不断升高，热量通过压电效应做功，实现了热量从冷端到热端的输运。选择了现有的MLCC电容器作为核心元件开展电卡原型致冷器件的探索，通过电卡致冷和机械做功，通过Brayton循环将热量从冷端输运到热端，实现了冷端温度的降低，大致为0.6K左右，实现了电卡原型致冷器件设计和验证的目的。