Problems and Solutions in Quantitative Analysis of Complex Mixtures by X-Ray Powder Diffraction

1987 ◽  
Vol 31 ◽  
pp. 295-308 ◽  
Author(s):  
David L. Bish ◽  
Steve J. Chipera
Keyword(s):  
Quantitative Analysis ◽  
Amorphous Materials ◽  
Rietveld Method ◽  
Internal Standard ◽  
Preferred Orientation ◽  
Complex Mixtures ◽  
Calibration Data ◽  
Cell Parameters ◽  
Amorphous Phases ◽  
Standard Data

AbstractIn spite of the wide availability of automated diffractometers and advanced data reduction software, numerous traditional problems still exist that make highly precise and accurate quantitative analyses of complex mixtures difficult. The problems include particle statistics, primary extinction, microabsorption, preferred orientation, overlapping and broad reflections, variation in standard data with composition, availability of pure standards, and detection of amorphous and trace phases. Our analyses of rocks use the matrix flushing method on < 5μm particle-size material mixed with a 1.0-μm corundum internal standard to minimize the first four effects. Integrated intensities are used, and we employ several peaks from each phase whenever possible. We overcame overlap problems through iterative calculations using integral, multiple peaks or with profile refinement. Use of observed and calculated diffraction patterns for every phase enables us to predict the effects of composition and preferred orientation on RIRs. This allows us to correct for these effects if reference intensity ratios (RIRs) are known as a function of composition and orientation. Detection of amorphous phases is a significant problem, and standard mixtures reveal that amounts of amorphous components below 30% are difficult to detect. The poor detection limit and the nature of the diffraction band from amorphous phases make internal standard or spiking methods the best approach for analyzing samples containing amorphous materials. The Rietveld method of quantitative analysis has the potential to minimize all of the above problems. This method requires a knowledge of the crystal structures of all component crystalline phases, but no calibration data are necessary, structural and cell parameters can be varied during the refinement process, so that compositional effects can be accommodated and precise cell parameters can be obtained for every phase. Since this method fits the entire diffraction pattern and explicitly uses all reflections from every phase, complex, overlapped patterns can be easily analysed. In addition, this method presents the opportunity to correct for preferred orientation and microabsorption during data analysis.

Quantitative Analysis of Cement-Based Materials and Sulfate Attack Products by XRD-Rietveld Analysis

2013 ◽  
Vol 357-360 ◽  
pp. 1362-1369 ◽  
Author(s):  
Hua Li ◽  
Jia Ping Liu ◽  
Wei Sun
Keyword(s):  
Quantitative Analysis ◽  
Calcium Hydroxide ◽  
Rietveld Method ◽  
Internal Standard ◽  
Rietveld Analysis ◽  
Sulfate Attack ◽  
Practical Significance ◽  
Cement Pastes ◽  
Cement Based Materials ◽  
Mixed Samples

XRD-Rietveld method has been adopted for quantitative analysis of phases in cement powder, phases in mixed samples of cement and pure calcium hydroxide, and sulfate attack products in cement pastes, based on the TOPAS software. The results show that, Rietveld analysis values show good agreement with the actual levels of mixed samples, and the accuracy degree of Rietveld method is at least as well as that of TG/DSC method which is commonly used in quantitative analysis of calcium hydroxide. By adding appropriate internal standard substance, XRD-Rietveld analysis method can be effectively used in quantitative analysis of sulfate attack products in cement-based materials. This work has practical significance on the study of sulfate attack of cement-based material.

Quantitative Analysis of Crystalline and Amorphous Phases in Glass–Ceramic Composites Like LTCC by the Rietveld Method

2006 ◽  
Vol 89 (8) ◽  
pp. 2632-2637 ◽  
Author(s):  
Stefan Kemethmuller ◽  
Andreas Roosen ◽  
Friedlinde Goetz-Neunhoeffer ◽  
Jurgen Neubauer
Keyword(s):  
Quantitative Analysis ◽  
Glass Ceramic ◽  
Rietveld Method ◽  
Ceramic Composites ◽  
Amorphous Phases

FULLPAT: a full-pattern quantitative analysis program for X-ray powder diffraction using measured and calculated patterns

2002 ◽  
Vol 35 (6) ◽  
pp. 744-749 ◽  
Author(s):  
Steve J. Chipera ◽  
David L. Bish
Keyword(s):  
Quantitative Analysis ◽  
Matrix Effects ◽  
Internal Standard ◽  
Solid Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Amorphous Phases ◽  
Quantitative Analysis Method ◽  
Diffraction Patterns ◽  
User Intervention

FULLPATis a quantitative X-ray diffraction methodology that merges the advantages of existing full-pattern fitting methods with the traditional reference intensity ratio (RIR) method. Like the Rietveld quantitative analysis method, it uses complete diffraction patterns, including the background. However,FULLPATcan explicitly analyze all phases in a sample, including partially ordered or amorphous phases such as glasses, clay minerals, or polymers. Addition of an internal standard to both library standards and unknown samples eliminates instrumental and matrix effects and allows unconstrained analyses to be conducted by direct fitting of library standard patterns to each phase in the sample. Standard patterns may include data for any solid material including glasses, and calculated patterns may also be used. A combination of standard patterns is fitted to observed patterns using least-squares minimization, thereby reducing user intervention and bias.FULLPAThas been coded into MicrosoftEXCELusing standard spreadsheet functions.

scholarly journals Fast quantitative analysis of the amorphous content with the Rietveld method

2014 ◽  
Vol 70 (a1) ◽  
pp. C949-C949
Author(s):  
Jordi Ibanez ◽  
Jose Fernandez-Turiel ◽  
Josep Elvira ◽  
Marta Rejas ◽  
Soledad Alvarez
Keyword(s):  
Rietveld Method ◽  
Internal Standard ◽  
Basic Research ◽  
Rietveld Analysis ◽  
Glassy Matrix ◽  
Fly Ashes ◽  
Amorphous Phases ◽  
Amorphous Content ◽  
Processing Times ◽  
Volcanic Ashes

The characterization of the mineralogy and chemical composition of multi-phase mixtures is of chief importance in many different contexts, from industry to basic research. In the case of industrial processes, it is often necessary to perform fast and reliable quantitative phase analyses (QPAs) in large amounts of samples that contain amorphous phases. Rietveld refinement from powder x-ray diffraction (XRD) data is widely employed for this purpose. The quantification of the amorphous content with the Rietveld method is usually performed by spiking the samples with an internal standard, and this implies increased processing times. Alternatively, in samples exhibiting the typical, broad XRD signal from the amorphous (glassy) matrix, a poorly-crystalline structure can be used to represent the amorphous phase during the Rietveld analysis [1]. This procedure provides highly consistent data, but is limited because the particular crystal structure used for the QPAs is strongly sample dependent. Recently, it has been shown that fast Rietveld QPAs of coal fly ashes can be carried out with no sample spiking by initially calibrating the XRD signal from the glass [2]. In this work, we evaluate the usefulness of the calibration Rietveld-based approach on two different types of samples: fly ashes from coal combustion plants, and volcanic ashes. While the mineralogy of the fly ashes considered here is relatively simple (they mainly contain quartz, mullite and glass), the volcanic ashes contain sizable amounts of crystalline compounds with both simple and complex structures, including quartz, feldspars, biotite, pyroxene or iron oxides. We show that the calibration approach provides a suitable method to assess in a fast and consistent manner the amount of crystalline and amorphous phases in both types of samples. This method may be extended to industrial characterization processes involving large numbers of complex samples, reducing considerably the analytical times.

Crystal structure of Nd2−xMxRu2O7−y (M=Cu, Ag) pyrochlores by X-ray powder diffraction

2007 ◽  
Vol 22 (3) ◽  
pp. 231-235 ◽  
Author(s):  
G. Kimmel ◽  
H. On ◽  
D. Itzhak ◽  
J. Hormadaly
Keyword(s):  
Powder Diffraction ◽  
Single Phase ◽  
Rietveld Method ◽  
Internal Standard ◽  
Pyrochlore Structure ◽  
Peak Position ◽  
X Ray ◽  
Cell Parameters ◽  
Ruthenium Oxides ◽  
Phase Structures

The crystal structures of ruthenium oxides with the general formula Nd2−xMxRu2O7−y, where M is Cu or Ag, 0≤x≤0.25, were investigated. All compounds that were prepared exhibit the pyrochlore structure with a cubic unit cell. The compounds were characterized by X-ray powder diffraction, and single-phase structures were found for Nd2−xCuxRu2O7−y, x=0.1, 0.2, 0.25, and for Nd2−xAgxRu2O7−y, x=0.1, 0.15, 0.2. The relative metal concentrations were verified by EDS. The cell parameters were determined by advanced peak-position analysis and calibrated by a Si internal standard. Atomic positions and oxygen occupancies where refined by the Rietveld method. It was found that the cell-size modifications agree with the relations between ionic sizes.

Determination of the crystallized fractions of a largely amorphous multiphase material by the Rietveld method

2001 ◽  
Vol 34 (2) ◽  
pp. 114-118 ◽  
Author(s):  
X. Orlhac ◽  
C. Fillet ◽  
P. Deniard ◽  
A. M. Dulac ◽  
R. Brec
Keyword(s):  
Rietveld Method ◽  
Amorphous Material ◽  
Effective Means ◽  
Site Occupancy ◽  
Internal Standard ◽  
Ceramic Materials ◽  
Contrast Effects ◽  
Crystalline Phases ◽  
Cell Parameters ◽  
High Level

The Rietveld method has proved to be a very effective means to characterize and quantify the crystalline phases and the amorphous phase in glass ceramic materials using X-ray powder diffraction data. The technique was applied to a borosilicate glass of the type used for high-level nuclear-waste containment, in order to measure the proportions of the crystallized phases after heat treatment and, thus, to qualify the thermal stability of the glass. Six crystalline phases were analysed in this way in an almost entirely (>95 wt%) amorphous material after adding a known proportion of an internal standard (TiO2). The quantitative analyses were corrected to allow for microabsorption effects resulting from grain-size and absorption-contrast effects. In addition to the quantitative data, unit-cell parameters and site-occupancy refinements revealed solid-solution and substitution phenomena in the crystal.

A standardless method of quantitative ceramic analysis using X-ray powder diffraction

1999 ◽  
Vol 32 (3) ◽  
pp. 381-386 ◽  
Author(s):  
Sujata Mazumdar
Keyword(s):  
Powder Diffraction ◽  
Crystalline Phase ◽  
Quantitative Estimation ◽  
Internal Standard ◽  
Ceramic Materials ◽  
Calibration Data ◽  
Ceramic Analysis ◽  
X Ray ◽  
Amorphous Phases ◽  
Programming Techniques

A new procedure using X-ray powder diffraction data for quantitative estimation of the crystalline as well as the amorphous phase in ceramics is described. Classification of the crystalline and amorphous X-ray scattering was achieved by comparison of the slopes at two successive points of the powder pattern at scattering angles at which the crystalline and amorphous phases superimpose. If the second slope exceeds the first by a stipulated value, the intensity is taken as crystalline; otherwise the scattering is considered as amorphous. Crystalline phase analysis is obtained by linear programming techniques using the concept that each observed X-ray diffraction peak has contributions fromncomponent phases, the proportionate analysis of which is required. The method does not require the measurement of calibration data for use as an internal standard, but knowledge of the approximate crystal structure of each phase of interest in the mixture is necessary. The technique is also helpful in qualitative analysis because each suspected phase is characterized by the probability that it will be present when a reflection zone is considered in which the suspected crystalline phase could contribute. The amorphous phases are determined prior to the crystalline ones. The method is applied to ceramic materials and some results are presented.

scholarly journals Exploitation of HPLC Analytical Method for Simultaneous Determination of Six Principal Unsaturated Fatty Acids in Oviductus Ranae Based on Quantitative Analysis of Multi-Components by Single-Marker (QAMS)

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 479
Author(s):  
Shihan Wang ◽  
Yuanshuai Gan ◽  
Hong Kan ◽  
Xinxin Mao ◽  
Yongsheng Wang
Keyword(s):  
Fatty Acids ◽  
Quantitative Analysis ◽  
Unsaturated Fatty Acids ◽  
Internal Standard ◽  
Active Components ◽  
Reliable Determination ◽  
External Standard Method ◽  
Single Marker ◽  
Oviductus Ranae

As one of the featured products in northeast China, Oviductus Ranae has been widely used as a nutritious food, which contains a variety of bioactive unsaturated fatty acids (UFAs). It is necessary to establish a scientific and reliable determination method of UFA contents in Oviductus Ranae. In this work, six principal UFAs in Oviductus Ranae, namely eicosapentaenoic acid (EPA), linolenic acid (ALA), docosahexaenoic acid (DHA), arachidonic acid (ARA), linoleic acid (LA) and oleic acid (OA), were identified using UPLC-MS/MS. The UFAs identified in Oviductus Ranae were further separated based on the optimized RP-HPLC conditions. Quantitative analysis of multi-components by single-marker (QAMS) method was implemented in content determination of EPA, ALA, DHA, ARA and OA, where LA was used as the internal standard. The experiments based on Taguchi design verified the robustness of the QAMS method on different HPLC instruments and chromatographic columns. The QAMS and external standard method (ESM) were used to calculate the UFA content of 15 batches of Oviductus Ranae samples from different regions. The relative error (r < 0.73%) and cosine coefficient showed that the two methods obtained similar contents, and the method validations met the requirements. The results showed that QAMS can comprehensively and effectively control the quality of UFAs in Oviductus Ranae which provides new ideas and solutions for studying the active components in Oviductus Ranae.

X-ray powder diffraction data of LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites

2021 ◽  
pp. 1-6
Author(s):  
Mariana M. V. M. Souza ◽  
Alex Maza ◽  
Pablo V. Tuza
Keyword(s):  
Crystal Structure ◽  
Rietveld Method ◽  
Pechini Method ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Modified Pechini Method ◽  
Scanning Electron

In the present work, LaNi0.5Ti0.45Co0.05O3, LaNi0.45Co0.05Ti0.5O3, and LaNi0.5Ti0.5O3 perovskites were synthesized by the modified Pechini method. These materials were characterized using X-ray fluorescence, scanning electron microscopy, and powder X-ray diffraction coupled to the Rietveld method. The crystal structure of these materials is orthorhombic, with space group Pbnm (No 62). The unit-cell parameters are a = 5.535(5) Å, b = 5.527(3) Å, c = 7.819(7) Å, V = 239.2(3) Å3, for the LaNi0.5Ti0.45Co0.05O3, a = 5.538(6) Å, b = 5.528(4) Å, c = 7.825(10) Å, V = 239.5(4) Å3, for the LaNi0.45Co0.05Ti0.5O3, and a = 5.540(2) Å, b = 5.5334(15) Å, c = 7.834(3) Å, V = 240.2(1) Å3, for the LaNi0.5Ti0.5O3.

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