对不同热处理状态下的微观组织结构进行了研究。采用物理化学相分析技术研究了9Cr13Mo3Co3Nb2V退火、淬火以及最终热处理制度下析出相的类型、含量及组成结构式。并用X射线小角散射(SAXS)(sm all angle x-ray scatter)分析了不同热处理...对不同热处理状态下的微观组织结构进行了研究。采用物理化学相分析技术研究了9Cr13Mo3Co3Nb2V退火、淬火以及最终热处理制度下析出相的类型、含量及组成结构式。并用X射线小角散射(SAXS)(sm all angle x-ray scatter)分析了不同热处理制度下析出相在不同粒度间隔中的质量分布。结果表明:①9Cr13Mo3Co3Nb2V钢退火状态的组织为珠光体+碳化物(M23C6,MC和M6C),淬火状态组织为马氏体+碳化物(M23C6和MC),最终热处理状态的组织为回火马氏体+碳化物(M23C6,MC和M3C);②小颗粒(≤300nm)碳化物析出相粒度分析表明,9Cr13Mo3Co3Nb2V钢退火、淬火状态析出相平均粒度相差不大,粗大颗粒较多,而最终热处理状态的析出相平均粒度明显减小,且细小颗粒比例较大。展开更多
Dipolar relaxation and dielectric/piezoelectric resonance in a (001)-cut Pb(Zn1/3Nb2/3)0.9Ti0.1O3 (PZNT10%) single crystal before and after electric (E)-field poling were presented. Dielectric permittivities were meas...Dipolar relaxation and dielectric/piezoelectric resonance in a (001)-cut Pb(Zn1/3Nb2/3)0.9Ti0.1O3 (PZNT10%) single crystal before and after electric (E)-field poling were presented. Dielectric permittivities were measured as functions of temperature, frequency and poling E-field strength. Frequency-dependent dielectric spectroscopy in the poled sample exhibits multiple piezoelectric resonances between 0.1 and 1 MHz, which can be described by the forced-damped-oscillator model. The resonant spectra show significant changes while phase transitions are taking place. The unpoled crystal shows almost no optical birefringence, indicating that the average structure symmetry is isotropic. Birefringence of the crystal is significantly enhanced by a prior E-field poling.展开更多
The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo...The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo- response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.展开更多
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
文摘对不同热处理状态下的微观组织结构进行了研究。采用物理化学相分析技术研究了9Cr13Mo3Co3Nb2V退火、淬火以及最终热处理制度下析出相的类型、含量及组成结构式。并用X射线小角散射(SAXS)(sm all angle x-ray scatter)分析了不同热处理制度下析出相在不同粒度间隔中的质量分布。结果表明:①9Cr13Mo3Co3Nb2V钢退火状态的组织为珠光体+碳化物(M23C6,MC和M6C),淬火状态组织为马氏体+碳化物(M23C6和MC),最终热处理状态的组织为回火马氏体+碳化物(M23C6,MC和M3C);②小颗粒(≤300nm)碳化物析出相粒度分析表明,9Cr13Mo3Co3Nb2V钢退火、淬火状态析出相平均粒度相差不大,粗大颗粒较多,而最终热处理状态的析出相平均粒度明显减小,且细小颗粒比例较大。
文摘Dipolar relaxation and dielectric/piezoelectric resonance in a (001)-cut Pb(Zn1/3Nb2/3)0.9Ti0.1O3 (PZNT10%) single crystal before and after electric (E)-field poling were presented. Dielectric permittivities were measured as functions of temperature, frequency and poling E-field strength. Frequency-dependent dielectric spectroscopy in the poled sample exhibits multiple piezoelectric resonances between 0.1 and 1 MHz, which can be described by the forced-damped-oscillator model. The resonant spectra show significant changes while phase transitions are taking place. The unpoled crystal shows almost no optical birefringence, indicating that the average structure symmetry is isotropic. Birefringence of the crystal is significantly enhanced by a prior E-field poling.
基金supported by the National Natural Sciences Foundation of China(Grant No.59995520)the National“863”High Technology Research and Development Program of China(Grant No.2001AA325030)the National“973”Key Basic Program of China(Grant No.2002CB613307)
文摘The piezoresponse behavior dependence of the Pb(Mg1/3Nb2/3)O3-30%PbTiO3 single crystal on the vacuum degree has been investigated by scanning force microscopy in the piezoresponse mode under high vacuum. Unusual piezo- response behavior related to the screening charges compensation mechanism is observed on the (111) crystal face. The significant piezoresponse degradation behavior with low piezoresponse signal under high vacuum is attributed to the instability of the polarization state due to the insufficient compensation of the intrinsic screening charges for the polarization charges in PMN-30%PT single crystal. In contrast, the remarkable domain contrast of the sample at ambient pressure is owing to the dominant surface screening charges deriving from surface adsorption, which plays an important role in determining the stability of the domain behavior and in achieving the optimal properties.
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.
