Fitting of full X-ray diffraction patterns is an effective method for quantifying abundances during X-ray diffraction (XRD) analyses. The method is based on the principal that the observed diffraction pattern is the s...Fitting of full X-ray diffraction patterns is an effective method for quantifying abundances during X-ray diffraction (XRD) analyses. The method is based on the principal that the observed diffraction pattern is the sum of the individual phases that compose the sample. By adding an internal standard (usually corundum) to both the observed patterns and to those for individual pure phases (standards), all patterns can all be normalized to an equivalent intensity based on the internal standard intensity. Using least-squares refinement, the individual phase proportions are varied until an optimal match is reached. As the fitting of full patterns uses the entire pattern, including background, disordered and amorphous phases are explicitly considered as individual phases, with their individual intensity profiles or “amorphous humps” included in the refinement. The method can be applied not only to samples that contain well-ordered materials, but it is particularly well suited for samples containing amorphous and/or disordered materials. In cases with extremely disordered materials where no crystal structure is available for Rietveld refinement or there is no unique intensity area that can be measured for a traditional RIR analysis, full-pattern fitting may be the best or only way to readily obtain quantitative results. This approach is also applicable in cases where there are several coexisting highly disordered phases. As all phases are considered as discrete individual components, abundances are not constrained to sum to 100%.展开更多
Nanoscale Sb doped titanium dioxide thin films photocatalyst （Ti1-xSbO2） were obtained from dip-coating sol-gel method. The influence of dopant Sb density on the crystal structure and the phase transformation of the...Nanoscale Sb doped titanium dioxide thin films photocatalyst （Ti1-xSbO2） were obtained from dip-coating sol-gel method. The influence of dopant Sb density on the crystal structure and the phase transformation of the thin tilms were characterized by X-ray diffraction （XRD） and Raman spectra. The results of XRD showed that as prepared lilms were not only in anatase state but also in brookite. The crystalline size was estimated to be around 13.3-20 nm. Raman spectra indicated there coexisted other phases and a transformation from brookite to anatase in the samples doped with 0.2% Sb. After doping a proper amount of Sb, the cryst,allization rate and the content of the anatase Ti1-x, SbO2 in the thin films was clearly enhanced because Sb replaced part. of the Ti of TiO2 in the thin films. The anode current density （photocurrent density） and the first order reaction speed constant （k） of t.hin films doped with 0.2% Sb reached 42.49 μA/cm^2 and 0.171 h/cm^2 under 254 nm UV illumination, respectively, which is about 11 times and 2 times that of the non doped TiO2 anode prepared by the same method respectively.展开更多
湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封...湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封闭咸水湖泊巴木错沉积物为研究对象,系统分析、评估了参比强度比(RIR)法和Rietveld全谱拟合法在复杂沉积物矿物定量分析中的可靠性和应用效果。文章采用高纯度刚玉作为内标物质,设计了1∶1、3∶7和1∶9三组不同配比的混合样品,通过X射线衍射(XRD)分析获取了完整的衍射数据。基于COD晶体结构数据库,分别采用RIR值法和Rietveld全谱拟合法进行定量计算,并结合非晶含量测定方法,构建了完整的矿物定量分析体系。研究结果表明,Rietveld全谱拟合法表现出优异的分析精度和稳定性:对于含量大于20%的主量相,相对标准偏差(RSD,Relative Standard Deviation)控制在3%以内;含量在5%~20%之间的次量相,RSD值保持在5%~10%范围内;即使对于含量低于5%的微量相,其定量结果也显著优于RIR值法。特别是在处理非均质样品时,Rietveld法表现出良好的适应性,各矿物相含量与混合比例呈现显著的线性相关性(R^(2)>0.95)。相比之下,RIR值法在高含量内标条件下(50%和30%)表现出显著的不稳定性,定量结果的相对偏差超出了SY/T5163-2018标准规定的允许范围。这种局限性主要源于其对单个衍射峰强度比值的过度依赖,易受样品基体效应和优势相干扰的影响。此外,通过非晶含量计算,获得了原始沉积物样品中约31%的非晶态物质含量,三组混合样品计算结果的高度一致性(RSD<3%)进一步验证了Rietveld法的可靠性。该研究不仅系统评估了两种定量方法的适用性,而且在复杂湖泊沉积物分析中首次实现了晶质矿物和非晶质组分的协同定量。研究结果对完善湖泊沉积物矿物定量分析方法,提高环境重建的准确性具有重要意义和应用价值。展开更多
以MgO和Nb2O5为原料,用高能球磨法制备Mg4Nb2O9前驱体,前驱体经900℃热处理合成Mg4Nb2O9纳米粉体.采用X射线衍射和扫描电镜(Scanning Electron Microscopy,SEM)研究了粉体随合成温度、球磨时间、保温时间的微结构变化和物相转变过程.结...以MgO和Nb2O5为原料,用高能球磨法制备Mg4Nb2O9前驱体,前驱体经900℃热处理合成Mg4Nb2O9纳米粉体.采用X射线衍射和扫描电镜(Scanning Electron Microscopy,SEM)研究了粉体随合成温度、球磨时间、保温时间的微结构变化和物相转变过程.结果表明,MgO-Nb2O5混合物经60 h高能球磨在900℃保温3 h合成出粒径为50~80 nm的Mg4Nb2O9纳米粉体.高能球磨法制备的粉体在1 200℃可烧结成致密的具有优异性能的Mg4Nb2O9陶瓷.展开更多
文摘Fitting of full X-ray diffraction patterns is an effective method for quantifying abundances during X-ray diffraction (XRD) analyses. The method is based on the principal that the observed diffraction pattern is the sum of the individual phases that compose the sample. By adding an internal standard (usually corundum) to both the observed patterns and to those for individual pure phases (standards), all patterns can all be normalized to an equivalent intensity based on the internal standard intensity. Using least-squares refinement, the individual phase proportions are varied until an optimal match is reached. As the fitting of full patterns uses the entire pattern, including background, disordered and amorphous phases are explicitly considered as individual phases, with their individual intensity profiles or “amorphous humps” included in the refinement. The method can be applied not only to samples that contain well-ordered materials, but it is particularly well suited for samples containing amorphous and/or disordered materials. In cases with extremely disordered materials where no crystal structure is available for Rietveld refinement or there is no unique intensity area that can be measured for a traditional RIR analysis, full-pattern fitting may be the best or only way to readily obtain quantitative results. This approach is also applicable in cases where there are several coexisting highly disordered phases. As all phases are considered as discrete individual components, abundances are not constrained to sum to 100%.
文摘Nanoscale Sb doped titanium dioxide thin films photocatalyst （Ti1-xSbO2） were obtained from dip-coating sol-gel method. The influence of dopant Sb density on the crystal structure and the phase transformation of the thin tilms were characterized by X-ray diffraction （XRD） and Raman spectra. The results of XRD showed that as prepared lilms were not only in anatase state but also in brookite. The crystalline size was estimated to be around 13.3-20 nm. Raman spectra indicated there coexisted other phases and a transformation from brookite to anatase in the samples doped with 0.2% Sb. After doping a proper amount of Sb, the cryst,allization rate and the content of the anatase Ti1-x, SbO2 in the thin films was clearly enhanced because Sb replaced part. of the Ti of TiO2 in the thin films. The anode current density （photocurrent density） and the first order reaction speed constant （k） of t.hin films doped with 0.2% Sb reached 42.49 μA/cm^2 and 0.171 h/cm^2 under 254 nm UV illumination, respectively, which is about 11 times and 2 times that of the non doped TiO2 anode prepared by the same method respectively.
文摘湖泊沉积物作为重要的环境演化记录载体,其矿物组合特征蕴含了丰富的古环境信息。然而,由于沉积物中晶质和非晶质组分的复杂共存关系,以及多相矿物体系的相互干扰效应,其精确定量分析一直是沉积学研究中的技术难点。该研究以西藏中部封闭咸水湖泊巴木错沉积物为研究对象,系统分析、评估了参比强度比(RIR)法和Rietveld全谱拟合法在复杂沉积物矿物定量分析中的可靠性和应用效果。文章采用高纯度刚玉作为内标物质,设计了1∶1、3∶7和1∶9三组不同配比的混合样品,通过X射线衍射(XRD)分析获取了完整的衍射数据。基于COD晶体结构数据库,分别采用RIR值法和Rietveld全谱拟合法进行定量计算,并结合非晶含量测定方法,构建了完整的矿物定量分析体系。研究结果表明,Rietveld全谱拟合法表现出优异的分析精度和稳定性:对于含量大于20%的主量相,相对标准偏差(RSD,Relative Standard Deviation)控制在3%以内;含量在5%~20%之间的次量相,RSD值保持在5%~10%范围内;即使对于含量低于5%的微量相,其定量结果也显著优于RIR值法。特别是在处理非均质样品时,Rietveld法表现出良好的适应性,各矿物相含量与混合比例呈现显著的线性相关性(R^(2)>0.95)。相比之下,RIR值法在高含量内标条件下(50%和30%)表现出显著的不稳定性,定量结果的相对偏差超出了SY/T5163-2018标准规定的允许范围。这种局限性主要源于其对单个衍射峰强度比值的过度依赖,易受样品基体效应和优势相干扰的影响。此外,通过非晶含量计算,获得了原始沉积物样品中约31%的非晶态物质含量,三组混合样品计算结果的高度一致性(RSD<3%)进一步验证了Rietveld法的可靠性。该研究不仅系统评估了两种定量方法的适用性,而且在复杂湖泊沉积物分析中首次实现了晶质矿物和非晶质组分的协同定量。研究结果对完善湖泊沉积物矿物定量分析方法,提高环境重建的准确性具有重要意义和应用价值。
