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
The effect of Sn^4＋ （BaSnO3） B-site substitution on the microstructure and dielectric properties of Ba（Mg1/3Ta2/3）O3 microwave ceramics was investigated. X-ray diffraction shows that a complex perovskite material...The effect of Sn^4＋ （BaSnO3） B-site substitution on the microstructure and dielectric properties of Ba（Mg1/3Ta2/3）O3 microwave ceramics was investigated. X-ray diffraction shows that a complex perovskite material Ba（Mg1/3Ta2/3）O3 was prepared. As Sn^4＋ content x increases in the （1-x） Ba（Mg1/3Ta2/3）O3-xBaSnO3 （x=0.00～0.20） system, the dielectric constant generally keeps unchanged, while TCF changes from positive to negative. Although the addition of Sn^4＋ reduces the ordering degree, Q f0 is still increased when the ceramics density increases. This trend implies that Q f0 of this system is mostly determined by ceramics density rather than ordering degree. After sintering at 1500℃ for 3 h, the system with x=0.15 was found to have excellent dielectric properties as follows：ε≈25, Q f0≥300,000 GHz at 7 GHz, TCF=-0.6×10^-6/℃.展开更多
Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN...Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na+ ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.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.
文摘The effect of Sn^4＋ （BaSnO3） B-site substitution on the microstructure and dielectric properties of Ba（Mg1/3Ta2/3）O3 microwave ceramics was investigated. X-ray diffraction shows that a complex perovskite material Ba（Mg1/3Ta2/3）O3 was prepared. As Sn^4＋ content x increases in the （1-x） Ba（Mg1/3Ta2/3）O3-xBaSnO3 （x=0.00～0.20） system, the dielectric constant generally keeps unchanged, while TCF changes from positive to negative. Although the addition of Sn^4＋ reduces the ordering degree, Q f0 is still increased when the ceramics density increases. This trend implies that Q f0 of this system is mostly determined by ceramics density rather than ordering degree. After sintering at 1500℃ for 3 h, the system with x=0.15 was found to have excellent dielectric properties as follows：ε≈25, Q f0≥300,000 GHz at 7 GHz, TCF=-0.6×10^-6/℃.
文摘Commercially available niobium (V) oxide [Nb2O5], with barium acetate [Ba(CH3COO)2] and magnesium acetate [Mg(CH3COO)2-4H2O] was used as the starting material in the sol-gel process for preparing Ba(Mg1/3Nb2/3)O3 (BMN) nanopowders. At first, Nb2O5 reacted with melting sodium hydroxide and transformed into dispersible oxide. The resulting glassy substance after cooling was dispersed and washed several times in distilled water to remove the Na+ ions. The as-prepared colloidal Nb2O5-nH2O was subsequently mixed with acetic solution of barium acetate and magnesium acetate according to the required molar proportions and followed by gelation. The ultrafine BMN powders were finally obtained after heat-treating the gel at 820℃for 1 h, and the as-sintered nanoceramics revealed a high relative density of 98.2%, and a high microwave Q-factor, of 10397 at 1.45GHz.
