失配应变对钛酸铅薄膜正负弹卡效应的影响

Study on the Misfit Strain’s Positive and Negative Elastocaloric Effect to Lead Titanate Thin Films

基于朗道-德文希尔理论,通过热力学分析,描述了钛酸铅薄膜的正负弹卡效应与应力场的关系,以及失配应变对钛酸铅薄膜正负弹卡效应的影响.结果表明,对钛酸铅薄膜施加不同应力场可以得到正负弹卡效应.失配应变对钛酸铅薄膜弹卡效应有较大的影响,拉伸失配应变增强钛酸铅薄膜负弹卡效应,拉伸失配应变为0.0004时使钛酸铅薄膜负弹卡效应温度变化峰值增大约2.3K,室温附近的温度变化增大约1.2K,同时温度变化的峰值向室温方向偏移约55℃;压缩失配应变对钛酸铅薄膜正弹卡效应有促进作用,压缩失配应变为-0.002时使钛酸铅薄膜正弹卡效应室温温度变化增大约1K.在失配应变调控下,同时利用钛酸铅薄膜正负弹卡效应,钛酸铅薄膜可以在室温附近获得约14K的温度改变,对于钛酸铅薄膜弹卡效应在固体制冷上的应用有重要意义.

Based on Landau-Devonshire theory,the relationship between the positive and negative elastocaloric effect of lead titanate thin film and stress field is obtained through thermodynamic analysis,and the effect of misfit strain on the positive and negative elastocaloric effect of lead titanate thin film is also obtained.The results show that the positive and negative elastocaloric effects can be obtained by applying different stress fields on lead titanate thin films.Misfit strain has a greater impact on elastocaloric effect of lead titanate thin films,negative elastocaloric effect can be enhanced by tensile misfit strain.The size of 0.000 4 tensile misfit strain increases temperature peak of negative elastocaloric effect of lead titanate thin film by about 2.3 K,the change of the near room temperature increases by about 1.2 K,at the same time,the peak of change on temperature shifts by 55 ℃ to the direction of room temperature.The compressive misfit strain has a certain promoting effect on the positive elastocaloric effect,making the room temperature change of the positive elastocaloric effect of lead titanate thin film increased by about 1 K.Under the misfit strain regulation,along with using positive and negative elastocaloric effect,lead titanate film can get about 14 K temperature change in the vicinity of room temperature.The application of lead titanate film elastocaloric effect is significant to solid refrigeration.