Ba(Mg1/3Nb2/3)O3(BMN)复合钙钛矿陶瓷具有高介电常数和高品质因子等介电性能,预示了其在光学领域的应用前景.本文采用第一性原理方法计算了BMN的电子结构,对其本征光学性能进行分析和预测.对固相合成六方相BMN的XRD测试结果进行Rietvel...Ba(Mg1/3Nb2/3)O3(BMN)复合钙钛矿陶瓷具有高介电常数和高品质因子等介电性能,预示了其在光学领域的应用前景.本文采用第一性原理方法计算了BMN的电子结构,对其本征光学性能进行分析和预测.对固相合成六方相BMN的XRD测试结果进行Rietveld精修(加权方差因子Rwp=6.73%,方差因子Rp=5.05%),在此基础上建立晶体结构模型并对其进行几何优化.运用基于密度泛函理论(DFT)的平面波赝势方法,对六方相BMN晶体模型的能带、态密度和光学性质进行理论计算.结果表明BMN的能带结构为间接带隙,禁带宽度Eg=2.728 e V.Mg-O和Ba-O以离子键结合为主,Nb-O以共价键结合为主,费米面附近的能带主要由O-2p和Nb-4d态电子占据,形成了d-p轨道杂化.修正带隙后,计算了BMN沿[100]和[001]方向上的复介电函数、吸收系数和反射率等光学性质.结果表明,BMN近乎光学各向同性,在可见光区,其本征透过率为77%<T<83%,折射率为1.91<n<2.14,并伴随一定的色散现象.实验测试结果与理论计算结果相吻合.展开更多
Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from pla...Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from plastic instability regions,and it was preferentially activated in vertical lamellae with a growth direction parallel to the compressive direction.Continuous dynamic recrystallization associated with lattice dislocations was the mechanism in both AuSn and Au5Sn multilayers.After spheroidization,strain accumulations were weakened in both of the equiaxed phases,and the deformation mechanism was substantially replaced by grain boundary sliding and migration.Based on these findings,hot rolling was conducted on an as-cast Au−20Sn alloy and a foil with a thickness of~50μm was successfully prepared.The present study can promote the development of Au−20Sn foils,and provide insights into the deformation behavior and microstructure evolution of multilayered eutectic alloys.展开更多
文摘Ba(Mg1/3Nb2/3)O3(BMN)复合钙钛矿陶瓷具有高介电常数和高品质因子等介电性能,预示了其在光学领域的应用前景.本文采用第一性原理方法计算了BMN的电子结构,对其本征光学性能进行分析和预测.对固相合成六方相BMN的XRD测试结果进行Rietveld精修(加权方差因子Rwp=6.73%,方差因子Rp=5.05%),在此基础上建立晶体结构模型并对其进行几何优化.运用基于密度泛函理论(DFT)的平面波赝势方法,对六方相BMN晶体模型的能带、态密度和光学性质进行理论计算.结果表明BMN的能带结构为间接带隙,禁带宽度Eg=2.728 e V.Mg-O和Ba-O以离子键结合为主,Nb-O以共价键结合为主,费米面附近的能带主要由O-2p和Nb-4d态电子占据,形成了d-p轨道杂化.修正带隙后,计算了BMN沿[100]和[001]方向上的复介电函数、吸收系数和反射率等光学性质.结果表明,BMN近乎光学各向同性,在可见光区,其本征透过率为77%<T<83%,折射率为1.91<n<2.14,并伴随一定的色散现象.实验测试结果与理论计算结果相吻合.
基金financial supports from the National Natural Science Foundation of China(Nos.U1502272,51901204)the Precious Metal Materials Genome Engineering in Yunnan Province,China(Nos.2019ZE001,202002AB080001)。
文摘Hot compression was performed on a multilayered Au−20Sn eutectic alloy to investigate the deformation behavior and microstructure evolution.During hot compression,microstructural spheroidization was initiated from plastic instability regions,and it was preferentially activated in vertical lamellae with a growth direction parallel to the compressive direction.Continuous dynamic recrystallization associated with lattice dislocations was the mechanism in both AuSn and Au5Sn multilayers.After spheroidization,strain accumulations were weakened in both of the equiaxed phases,and the deformation mechanism was substantially replaced by grain boundary sliding and migration.Based on these findings,hot rolling was conducted on an as-cast Au−20Sn alloy and a foil with a thickness of~50μm was successfully prepared.The present study can promote the development of Au−20Sn foils,and provide insights into the deformation behavior and microstructure evolution of multilayered eutectic alloys.
