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Rietveld refinement
About: Rietveld refinement is a research topic. Over the lifetime, 12836 publications have been published within this topic receiving 271353 citations.
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TL;DR: In this paper, the authors presented models compatible with the Rietveld method for the anisotropic broadening of the diffracted peaks produced by crystallite size and microstrain.
Abstract: Models are presented which are compatible with the Rietveld method for the anisotropic broadening of the diffracted peaks produced by crystallite size and microstrain. The models, derived from general crystallographic considerations, are different for different Laue groups.
560 citations
TL;DR: In this paper, the authors used Europium-doped nitride phosphors, Ca1-xEuxAlSiN3 (x = 0−0.2), for self-propagating high-temperature synthesis.
Abstract: Divalent europium-doped nitride phosphors, Ca1-xEuxAlSiN3 (x = 0−0.2), were successfully prepared by the self-propagating high-temperature synthesis (SHS) by using Ca1-xEuxAlSi alloy powder as a precursor. The Rietveld refinement analysis was carried out on the CaAlSiN3 host lattice to elucidate the luminescence properties of dopant Eu2+ on the tetrahedrally coordinated site. For the Eu2+ doped samples, strong absorption peaking at about 460 nm was observed on the excitation spectra, which matched perfectly with the current blue light of InGaN/GaN light-emitting diodes (LEDs). The optimized sample, Ca0.98Eu0.02AlSiN3, gave the red emission peaking at 649 nm of which the intensity was competitive with the sample prepared from the metal nitride raw materials (Ca3N2, AlN, Si3N4, and EuN). The CIE chromaticity index (0.647, 0.347) with high color saturation indicated that it was a promising candidate as a red-emitting phosphor for the InGaN/GaN-based down-conversion white LEDs for general illumination or disp...
514 citations
TL;DR: In this article, the superconducting phase diagram of NdFeAsO 1- y was established as a function of oxygen content, which was determined by Rietveld refinement.
Abstract: The crystal structure of LnFeAsO 1- y (Ln = La, Nd) has been studied by the powder neutron diffraction technique. The superconducting phase diagram of NdFeAsO 1- y is established as a function of oxygen content which is determined by Rietveld refinement. The small As–Fe bond length suggests that As and Fe atoms are connected covalently. FeAs 4 -tetrahedrons transform toward a regular shape with increasing oxygen deficiency. Superconducting transition temperatures seem to attain maximum values for regular FeAs 4 -tetrahedrons.
509 citations
TL;DR: In this paper, a quasi-2D LiNiO{sub 2}O and NiO was submitted to several thermal treatments, in order to determine the influence of the temperature on the composition.
Abstract: Lithium nickel oxide, used as the positive electrode in lithium batteries, crystallizes in the rhombohedral system (SG:R{bar 3}m) with a layered structure. In fact, stoichiometric LiNiO{sub 2} has never been reported. The true formula is Li{sub 1{minus}z}Ni{sub 1+z}O{sub 2} (0.00 < z < 0.20); z is dependent on the experimental conditions. This nonstoichiometry leads to a strong decrease of the battery performance. Therefore, several methods of preparation were investigated to synthesize stoichiometric LiNiO{sub 2}. The Li{sub 0.98}Ni{sub 1.02}O{sub 2} composition, which is very close to the ideal one, was obtained from a mixture of Li{sub 2}O and NiO heated at 700 C. This quasi-2D LiNiO{sub 2} was submitted to several thermal treatments, in order to determine the influence of the temperature on the composition. Purposely lithium deficient phases were also prepared. Correlations between the composition of each material (deduced from the Rietveld refinement of the X-ray diffraction pattern) and the magnetic and electrochemical behavior are discussed.
506 citations
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25 Apr 1992
TL;DR: The Rietveld method is described in this article, where structure and lattice parameters are directly refined from powder diffraction data and several functions such as extinction correction, preferred orientation, and profile shape function have been improved to give physical meanings to parameters contained in them.
Abstract: The outline of the Rietveld method is described where structure and lattice parameters are directly refined from powder diffraction data. Several functions such as extinction correction, preferred-orientation function, and profile-shape function, which are contained in the model function, have been improved to give physical meanings to parameters contained in them. Structure-refinement strategy is introduced which may be useful for beginners. Combined refinement of X-ray and neutron diffraction data is now being used more and more widely to extract structural information from powder patterns as much as possible.
502 citations