scholarly journals Role of chemical substitution in the photoluminescence properties of cerium samarium tungstates Ce(2-x)Smx (WO4)3 (0≤x≤0.3)

2020 ◽  
Vol 225 ◽  
pp. 01013
Author(s):  
K. Derraji ◽  
C. Favotto ◽  
J-C Valmalette ◽  
S. Villain ◽  
J-R. Gavarri ◽  
...  
Keyword(s):  
Solid Solution ◽  
Rietveld Analysis ◽  
Excitation Energies ◽  
Diffraction Profile ◽  
Vacancy Defects ◽  
X Ray ◽  
Cell Parameters ◽  
Structural Distortions ◽  
Ir Emission

In the general framework of the development of materials with tunable photoluminescence, a series of cerium samarium tungstates Ce(2-x)Smx(WO4)3 with x≤0.3 was synthesized by a coprecipitation method followed by thermal treatment at 1000 °C. The polycrystalline compounds were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence experiments. In the present work, the objective would be to determine the role of PL emitting centers in the variations of PL intensities. Firstly, Rietveld analysis showed a decrease of cell parameters and confirmed that a solid solution was obtained. Diffraction profile analyses showed that structural distortions increasing with composition x were observed: they were ascribed to difference in cation sizes of Ce3+ and Sm3+, and to defects generated during crystal growth. The photoluminescence (PL) spectra were obtained under X-Ray (45 kV-35 mA) and UV (364.5 nm) excitations. Two PL emissions of Ce3+ were observed only under UV excitation. Four PL emissions of Sm3+ were observed under UV and X-ray excitations, and their intensities decreased with increasing composition x. Two additional transitions were observed under UV and X-ray excitations: they were attributed to oxygen vacancy defects. In the range 800 to 1000 nm, an increasing IR emission is observed: it was ascribed to emissions due to other oxygen vacancies. The main results are reported in Table 1. The chromaticity diagram (see Figure 1) showed that the colors associated with PL responses vary with Sm composition and excitation energies. This offers the opportunity to develop materials with tunable PL. To better understand this complex behavior, now, we plan to study the solid solution in the composition range x>0.3.

Rietveld Analysis and Pair Wise Substitutional Alloys

1991 ◽  
Vol 35 (A) ◽  
pp. 63-68
Author(s):  
Wayne D. Kaplan ◽  
Giora Kimmel
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Comprehensive Model ◽  
Powder Diffraction Data ◽  
Unique Role ◽  
X Ray ◽  
Substitutional Alloys

AbstractRietveld Analysis on X-Ray powder diffraction data was used to build a comprehensive model of the structures in gallmm rich R-Ga systems (R is a rare earth between La and Gd). The ability to refine occupation factors as well as atomic positions allowed for the analysis of the e solid solution, its structural relation to the ordered ∊′ phase, and the unique role of the Ga-Ga pairs in these systems.

Towards a revisitation of vesuvianite-group nomenclature: the crystal structure of Ti-rich vesuvianite from Alchuri, Shigar Valley

2016 ◽  
Vol 72 (5) ◽  
pp. 744-752 ◽  
Author(s):  
Sergey M. Aksenov ◽  
Nikita V. Chukanov ◽  
Vyacheslav S. Rusakov ◽  
Taras L. Panikorovskii ◽  
Ramiza K. Rastsvetaeva ◽  
...  
Keyword(s):  
Octahedral Site ◽  
Structure Refinement ◽  
Optical Measurements ◽  
Transition Elements ◽  
X Ray ◽  
Cell Parameters ◽  
Tetragonal Unit Cell ◽  
Northern Areas ◽  
Shigar Valley

Vesuvianite containing 5.85 wt% TiO2from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement,27Al NMR,57Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are:a= 15.5326 (2),c= 11.8040 (2) Å, space groupP4/nnc. The structure was refined to finalR1= 0.031,wR2= 0.057 for 11247I> 2σ(I). A general crystal-chemical formula of studied sample can be written as follows (Z= 2):[8–9](Ca17.1Na0.9)[8]Ca1.0[5](Fe2+0.44Fe3+0.34Mg0.22)[6](Al3.59Mg0.41)[6](Al4.03Ti2.20Fe3+1.37Fe2+0.40) (Si18O68) [(OH)5.84O2.83F1.33]. The octahedral siteY2 is Al-dominant and does not contain transition elements. Another octahedral siteY3 is also Al-dominant and contains Fe2+, Fe3+and Ti. The siteY1 is split intoY1aandY1bpredominantly occupied by Fe2+and Fe3+, respectively. The role of theY1 site in the diversity of vesuvianite-group minerals is discussed.

A Simple Dissolved Metals Mixing Route to Prepare Nanostructured Mg0.8Zn0.2TiO3 Solid Solution

2015 ◽  
Vol 1112 ◽  
pp. 47-52 ◽  
Author(s):  
Frida Ulfah Ermawati ◽  
Suasmoro Suasmoro ◽  
Suminar Pratapa
Keyword(s):  
Solid Solution ◽  
Particle Size ◽  
Rietveld Analysis ◽  
Dissolved Metals ◽  
Intermediate Phases ◽  
Particle Size Analyzer ◽  
Ft Ir ◽  
Xrd Patterns ◽  
Zn Ions

A study of liquid mixing route to synthesize high purity Mg0.8Zn0.2TiO3 nanopowder, a candidate dielectric ceramics, has been successfully performed. Formation of the phases on the dried powder was studied using TG/DTA, XRD and FT-IR data. Rietveld analysis on the collected XRD patterns confirmed the formation of solid solution in the system. Such solid solution can be obtained from the powder calcined at 500 °C, but calcination at 550 °C gave rise to the most optimum molar purity up to 98.5% without intermediate phases. The role of Zn ions on the formation of solid solution was also discussed. Homogeneity of particle size distribution and nano-crystallinity of the system was verified from the particle size analyzer data, TEM image and the Rietveld analysis output.

Crystallochemistry and structural studies of two newly CaSb0.50Fe1.50(PO4)3 and Ca0.50SbFe(PO4)3 Nasicon phases

2006 ◽  
Vol 21 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Abderrahim Aatiq ◽  
My Rachid Tigha ◽  
Rabia Hassine ◽  
Ismael Saadoune
Keyword(s):  
Solid State ◽  
Room Temperature ◽  
Rietveld Analysis ◽  
Structural Studies ◽  
Hexagonal Cell ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Crystallographic Structures

Crystallographic structures of two new orthophosphates Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 obtained by conventional solid state reaction techniques at 900 °C, were determined at room temperature from X-ray powder diffraction using Rietveld analysis. The two compounds belong to the Nasicon structural family. The space group is R3 for Ca0.50SbFe(PO4)3 and R3c for CaSb0.50Fe1.50(PO4)3. Hexagonal cell parameters for Ca0.50SbFe(PO4)3 and CaSb0.50Fe1.50(PO4)3 are: a=8.257(1) Å, c=22.276(2) Å, and a=8.514(1) Å, c=21.871(2) Å, respectively. Ca2+ and vacancies in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3 are ordered within the two positions, 3a and 3b, of M1 sites. Structure refinements show also a quasi-ordered distribution of Sb5+ and Fe3+ ions within the Nasicon framework. Thus, in {[Ca0.50]3a[◻0.50]3b}M1SbFe(PO4)3, each Ca(3a)O6 octahedron shares two faces with two Fe3+O6 octahedra and each vacancy (◻(3b)O6) site is located between two Sb5+O6 octahedra. In [Ca]M1Sb0.50Fe1.50(PO4)3 compound (R3c space group), all M1 sites are occupied by Ca2+ and the Sb5+ and Fe3+ ions are randomly distributed within the Nasicon framework.

The solid solution TbNiIn1−x Ga x

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Myroslava Horiacha ◽  
Galyna Nychyporuk ◽  
Rainer Pöttgen ◽  
Vasyl Zaremba
Keyword(s):  
Solid Solution ◽  
Unit Cell ◽  
Type Structure ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Structure Space ◽  
Arc Melting

Abstract Phase formation in the solid solution TbNiIn1−x Ga x at 873 K was investigated in the full concentration range by means of powder X-ray diffraction and EDX analysis. The samples were synthesized by arc-melting of the pure metals with subsequent annealing at 873 K for one month. The influence of the substitution of indium by gallium on the type of structure and solubility was studied. The solubility ranges have been determined and changes of the unit cell parameters were calculated on the basis of powder X-ray diffraction data: TbNiIn1–0.4Ga0–0.6 (ZrNiAl-type structure, space group P 6 ‾ 2 m $P‾{6}2m$ , a = 0.74461(8)–0.72711(17) and c = 0.37976(5)–0.37469(8) nm); TbNiIn0.2–0Ga0.8–1.0 (TiNiSi-type structure, space group Pnma, а = 0.68950(11)–0.68830(12), b = 0.43053(9)–0.42974(6), с = 0.74186(10)–0.73486(13) nm). The crystal structures of TbNiGa (TiNiSi type, Pnma, a = 0.69140(5), b = 0.43047(7), c = 0.73553(8) nm, wR2=0.0414, 525 F 2 values, 21 variables), TbNiIn0.83(1)Ga0.17(1) (ZrNiAl type, P 6 ‾ 2 m $P‾{6}2m$ , a = 0.74043(6), c = 0.37789(3) nm, wR2 = 0.0293, 322 F 2 values, 16 variables) and TbNiIn0.12(2)Ga0.88(2) (TiNiSi type, Pnma, a = 0.69124(6), b = 0.43134(9), c = 0.74232(11) nm, wR2 = 0.0495, 516 F 2 values, 21 variables) have been determined. The characteristics of the solid solutions and the variations of the unit cell parameters are briefly discussed.

A new BaCa(CO3)2 polymorph

2019 ◽  
Vol 75 (3) ◽  
pp. 291-300
Author(s):  
Dominik Spahr ◽  
Lkhamsuren Bayarjargal ◽  
Victor Vinograd ◽  
Rita Luchitskaia ◽  
Victor Milman ◽  
...  
Keyword(s):  
Density Functional ◽  
Rietveld Analysis ◽  
Radioactive Isotopes ◽  
Synthesis Product ◽  
Monoclinic Space Group ◽  
Unit Cell Parameters ◽  
Functional Theory ◽  
Model Calculations ◽  
X Ray ◽  
Cell Parameters

A new polymorph of the double carbonate BaCa(CO3)2, `a C2 phase', has been synthesized. Its structure has been obtained by density-functional-theory-based (DFT-based) model calculations and has been refined by Rietveld analysis of X-ray powder diffraction data. The structure of the new polymorph differs significantly from those of the established polymorphs barytocalcite, paralstonite and alstonite. The unit-cell parameters of the new monoclinic (space group C2) compound are a = 6.6775 (5), b = 5.0982 (4), c = 4.1924 (3) Å, β = 109.259 (1)°. The new compound has been further characterized using Raman spectroscopy. This work shows that earlier studies have misidentified the products of an established synthesis route and that findings based on the incorrect identification of the synthesis product concerning the suitability of barytocalcite as a matrix for the retention of radioactive isotopes will need to be reconsidered.

Synthesis and structural characterization of ASnFe(PO4)3 (A=Na2,Ca,Cd) phosphates with the Nasicon type structure

2004 ◽  
Vol 19 (3) ◽  
pp. 272-279 ◽  
Author(s):  
Abderrahim Aatiq
Keyword(s):  
Room Temperature ◽  
Random Distribution ◽  
Rietveld Analysis ◽  
Type Structure ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Cell Parameters ◽  
Nasicon Type ◽  
Cationic Distribution

The crystal structures of ASnFe(PO4)3 (A=Na2, Ca, Cd) phases, obtained by conventional solid state reaction techniques at (950–1000 °C), were determined at room temperature from X-ray powder diffraction (XRD) using Rietveld analysis. The three materials exhibit the Nasicon-type structure (R3c space group, Z=6) with a random distribution of Sn(Fe) within the framework. Hexagonal cell parameters when A=Na2, Ca and Cd are: a=8.628(1) Å, c=22.151(2) Å; a=8.569(1) Å, c=22.037(2) Å and a=8.587(1) Å, c=21.653(2) Å, respectively. Structural refinements show a partial occupancy of M1 (Na(1)) and M2 (Na(2)) sites in Na2SnFe(PO4)3 leading to the cationic distribution [Na1.22□1.78]M2[Na0.78□0.22]M1SnFe(PO4)3. Ca2+ ions are distributed only in the M1 site of [□3]M2[Ca]M1SnFe(PO4)3. From XRD data, it is difficult to unambiguously distinguish between Cd2+ and Sn4+ ions in CdSnFe(PO4)3. Nevertheless the overall set of cation–anion distances within the Nasicon framework clearly shows that the cationic distribution can be illustrated by the [□3]M2[Cd]M1SnFe(PO4)3 crystallographic formula. Distortion within the [Sn(Fe)(PO4)3] frameworks, in ASnFe(PO4)3 (A=Na2,Ca,Cd) phases, is shown to be related to the M1 site size. © 2004 International Centre for Diffraction Data.

scholarly journals Umbite Type Zirconium Germanates for Cs Removal

MRS Advances ◽  
2017 ◽  
Vol 2 (13) ◽  
pp. 729-734 ◽  
Author(s):  
Ryan George ◽  
Joseph A. Hriljac
Keyword(s):  
Rietveld Analysis ◽  
Parent Material ◽  
High Yield ◽  
Synthesis Methods ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Natural Mineral ◽  
X Ray ◽  
Cell Parameters ◽  
Defect Sites

ABSTRACTPure and Nb-doped zirconium germanate materials of composition K2-xZr1-xNbxGe3O9.H2O where x = 0, 0.1, 0.2 and 0.3 with the structure of the natural mineral umbite have been prepared in high yield using hydrothermal synthesis methods. The parent material displays virtually no ion exchange of the K+ for Cs+ but the doped materials show rapidly enhanced exchange with replacement of ca. 70% of the K+ by Cs+ for the 30% doped material. Rietveld analysis of the powder X-ray diffraction data is consistent with no change in the unit cell parameters or K+ bonding prior to the exchange, hence we propose the improved property is due to the creation of cation defect sites within the pores of the material that facilities greater cation mobility and leads to exchange.

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