La掺杂AgSnO2触头材料热性能的第一性原理研究

First-Principles Study on Thermal Properties of La-doped AgSnO Contact Materials

针对稀有金属La原子掺杂对AgSnO2触头材料热性能的影响,采用密度泛函理论、第一性原理以及CASTEP软件对掺杂体系的热学性质进行了理论计算,得到了掺杂前后SnO2晶体的形成能、声子谱、声子态密度及分波态密度和相关热学参量,并对各计算结果和曲线图进行了理论分析。结果表明:掺杂不同浓度的La原子后,体系的形成能力具有较大差别,并结合声子谱曲线,当掺杂浓度为25%时,声子谱未出现虚频,说明此浓度下的掺杂体系能稳定存在。通过分析态密度图及分波态密度图可以得到,体系中La原子与O原子具有较强的耦合作用,即La原子的掺杂可以有效地激发O原子的活性,使参加热运动的分子数量增多,即热容较未掺杂体系得到明显提高。La的掺杂使SnO2晶体的熵、自由能及焓曲线变得明显陡峭,即体系的混乱度增加,晶体自由能降低,吸收的热量增加,从而提高了晶体的恢复能力,并对材料热导率的大小产生较大的影响。

According to the influence of La atom doping on the thermal properties of AgSnO2 contact materials,theoretical calculations were carried out by density functional theory,first-principle and CASTEP software. The formation energy,phonon spectrum,phonon state density and partial wave state density and related thermodynamic parameters of the SnO2 crystal before and after doping were obtained,and the calculation results and curves were analyzed theoretically. The results showed that the doped system had good forming ability. Combined with the phonon spectrum curve,when the doping concentration was 25%,the phonon spectrum did not show a virtual frequency,and the crystal could exist stably. Through the analysis of density of states and the density of partial wave states,La atoms and O atoms had a strong coupling effect,which effectively stimulated the activity of O atoms,which increased the number of molecules participating in motion,that was,the heat capacity was significantly improved compared with the undoped system. The doping of La made the entropy,free energy and enthalpy curve of the SnO2 crystal became steep,that was,the chaos of the system increased,the free energy of the crystal decreased,and the absorbed heat increased,which improved the recovery ability of the crystal and it also had a large effect on the thermal conductivity of the material.