铁电材料液氦温区比热是否存在T^3/2贡献？

项目名称： 铁电材料液氦温区比热是否存在T^3/2贡献？

项目编号： No.21473198

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 史全

作者单位： 中国科学院大连化学物理研究所

项目金额： 84万元

中文摘要： 上世纪70-80年代，美囯量热学家Lawless发现液氦温区铁电材料比热存在T^3/2贡献；该贡献被认为由材料的铁电性质引起，并称为Lawless Law。但随后，德国量热学家Gmelin认为，铁电材料比热T^3/2贡献并非源于材料的铁电性，而是材料中的晶格缺陷或杂质引起的。近年来，本项目申请人及其他一些研究者对某些新型铁电材料进行低温量热研究发现，其比热确实存在类似T^3/2的贡献。从而这又引起了铁电材料比热是否存在T^3/2贡献的争议。本项目拟利用当今国际上先进的综合物性测量系统（PPMS）在1.9至300K温区，精密测试和系统研究一系列铁电材料的比热性质，以验证该类材料的比热是否存在T^3/2贡献，从而解决学术界这一悬而未决的争议问题。与此同时，本项目亦利用PPMS研究一系列具有重要科学意义和应用前景的新型铁电材料的热力学性质，从而为该类功能材料的研发提供重要的基础数据和理论依据

中文关键词： 热化学；量热学；低温比热；铁电材料；综合物性测量系统(PPMS)

英文摘要： W.N.Lawless, a calorimetrist from the U.S., found in last 70' and 80' that some ferroelectrics could exhibit a T^3/2 contribution in their specific heats at liquid helium temperature region. This contribution was attributed to the intrinsic properties of ferroelectrics, which was also known as Lawless Law. In the following studies by E.Gmelin et al.,however,they indicated that this T^3/2 could not stem from the ferrolectirc property but the presense of defects or impurities.More recently, some researchers found in low temperature specific heat measreuments on some new ferroelectrics or those that have not been measured before,that the introduce of T^3/2 term can indeed improve the specific heat data fitting at liquid helium temperature region. Based on these facts, here is the questions again: Is there a T^3/2 contribution to the specific heat of ferroelectrics at low temperatures? In this project, we are planning to study the secific heats of a series of ferroelectrics using a Physical Property Measurement System (PPMS) in the temperature range from 1.9 K to 300 K, and fit the experimental data to the theoretical models and try to clarify this open question. Moreover, from this project, we could also provide thermodynamic studies on some new ferroelectrics, which may provide important experimental data for development and theoretical study of these materials.

英文关键词： Thermochemistry;Calorimetry;Low-Temperature Specific Heat;Ferroelectrics;Physical Property Measurement System (PPMS)