Structural and optical characterization of Er-doped CaMoO4 down-converting phosphors

2020 ◽  
Vol 76 (5) ◽  
pp. 926-938
Author(s):  
Puneet Kaur ◽  
Rajesh Kumar ◽  
Shreya Davessar ◽  
Atul Khanna
Keyword(s):  
Green Emission ◽  
Unit Cell ◽  
Potential Candidate ◽  
X Ray Diffraction ◽  
Tetragonal Crystal ◽  
Crystal Unit Cell ◽  
Tetragonal Crystal Structure ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Er Doped

xEr2O3–(1−x)CaMoO4 (x = 1, 3, 5, 7 and 10 mol%) nanoparticles were synthesized by solid-state sintering at 800°C. X-ray diffraction studies confirmed the tetragonal crystal structure of CaMoO4, while the doped samples show the co-existence of cubic Er2O3 and tetragonal CaMoO4 and rule out the replacement of Ca2+ by Er3+ in the structure. The crystal unit-cell dimensions, phase concentration and atomic position coordinates were determined by Rietveld refinement. The short-range structure of CaMoO4 consists of tetrahedral MoO4 and snub disphenoid deltahedral CaO8 units, while the unit cell of Er2O3 consists of two types of ErO6 octahedral units. All MoO4 units contain Mo—O bonds of equal lengths, whereas two types of slightly different Ca—O bond lengths exist in CaO8. Raman spectra of the doped samples show only Mo—O vibrational modes and the Raman peaks of Er2O3 are masked by Mo—O bond vibrations. CaMoO4 shows bluish-green emission at 500 nm, while Er-doped samples show strong green emission under UV excitation. UV irradiation (380 nm) induces down-conversion green emission at 531 nm and 552 nm and good color purity in 1 mol% Er2O3–CaMoO4 sample which makes it a potential candidate for applications in optical devices.

scholarly journals The crystal structures of two polyamides (‘nylons’)

1947 ◽  
Vol 189 (1016) ◽  
pp. 39-68 ◽  
Keyword(s):  
Crystal Structures ◽  
Unit Cell ◽  
Chain Molecule ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Dimensions ◽  
C Fibre ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Crystalline Forms

Detailed interpretations of the X -ray diffraction patterns of fibres and sheets of 66 and 6.10 polyamides (polyhexam ethylene adipamide and sebacamide respectively) are proposed. The crystal structures of the two substances are completely analogous. Fibres of these two polyam ides usually contain two different crystalline forms, α and β, which are different packings of geometrically similar molecules; most fibres consist chiefly of the α form. In the case of the 66 polymer, fibres have been obtained in which there is no detectable proportion of the β form. Unit cell dimensions and the indices of reflexions for the α form were determined by trial, using normal fibre photographs, and were checked by using doubly oriented sheets set at different angles to the X -ray beam. The unit cell of the a form is triclinic, with a — 4·9 A, b = 5·4 A, c (fibre axis) = 17·2A, α = 48 1/2º, β = 77º, γ = 63 1/2º for the 66 polymer; a = 4·95A, b = 5·4A, c (fibre axes) = 22·4A, α = 49º, β = 76 1/2º, γ = 63 1/2º for the 6.10 polymer. One chain molecule passes through the cell in both cases. Atomic coordinates in occrystals were determined by interpretation of the relative intensities of the reflexions. The chains are planar or very nearly so; the oxygen atoms appear to lie a little off the plane of the chain. The molecules are linked by hydrogen bonds between C = 0 and NH groups, to form sheets. A simple packing of these sheets of molecules gives the α arrangement.

Crystallization and preliminary X-ray diffraction studies of cytochrome c 6 from Porphyra yezoensis

2000 ◽  
Vol 56 (1) ◽  
pp. 79-80
Author(s):  
Tomokazu Sasaki ◽  
Megumi Nakahara ◽  
Aya Matsuda ◽  
Takenobu Yamasaki ◽  
Sakae Katoh ◽  
...  
Keyword(s):  
Porphyra Yezoensis ◽  
Unit Cell ◽  
Diffusion Method ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
Space Group ◽  
Cell Dimensions ◽  
Tetragonal Crystals ◽  
Tetragonal Form ◽  
Unit Cell Dimensions

Cytochrome c 6 from the red alga Porphyra yezoensis has been purified and crystallized by the sitting-drop vapour-diffusion method. Two different crystal forms, tetragonal and orthorhombic, were obtained. The tetragonal crystals belong to space group P41212 or P43212, with unit-cell dimensions a = 49.33 (2), c = 83.70 (10) Å. The orthorhombic crystals belong to space group P212121, with unit-cell dimensions a = 46.74 (2), b = 49.42 (1), c = 37.11 (1) Å. Absorption spectra of the crystals showed that the tetragonal form was oxidized and the orthorhombic form was reduced.

Unit cell dimensions of the hydrated aluminium phosphate–sulphate minerals sanjuanite, kribergite, and hotsonite

1989 ◽  
Vol 53 (371) ◽  
pp. 385-386 ◽  
Author(s):  
H. De Bruiyn ◽  
G. J. Beukes ◽  
W. A. Van Der Westhuizen ◽  
E. A. W. Tordiffe
Keyword(s):  
Unit Cell ◽  
X Ray Diffraction ◽  
Aluminium Phosphate ◽  
Powder Diffraction File ◽  
Cell Parameters ◽  
Cell Dimensions ◽  
Unit Cells ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Hydrated Aluminium

AT the time when the hydrated aluminium phosphate-sulphate hotsonite (Beukes et al., 1984a) and its equally rare relative zaherite (Beukes et al., 1984b; De Bruiyn et al., 1985) were discovered near Pofadder, South Africa, very little was known about the unit cells of the other two hydrated aluminium phosphate-sulphate minerals sanjuanite and kribergite, originally described by De Abeledo et al. (1968) from Argentina and Sweden, respectively. Although the Powder Diffraction file (PDF) contains the X-ray diffraction patterns for sanjuanite and kribergite (PDF 20-47 and 20-48 respectively), they had not been indexed nor have their unit cell parameters been calculated thus far.

Phase Relationships Involving RDX and Common Solid Propellant Binders

1995 ◽  
Vol 418 ◽  
Author(s):  
E. Boyer ◽  
P. W. Brown ◽  
K. K. Kuo
Keyword(s):  
Cell Volume ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Melting Temperatures ◽  
Triethyl Citrate ◽  
Cell Dimensions ◽  
The Common ◽  
Unit Cell Dimensions ◽  
Phase Relationships ◽  
Acetate Butyrate

AbstractThe solubilities of the common propellant ingredients acetyl triethyl citrate (ATEC) and cellulose acetate butyrate (CAB) and their effects on RDX (cyclotrimethylenetrinitramine) unit cell dimensions were investigated. If there is appreciable solid solubility, solutions will form and will have enthalpies of fusion, melting temperatures, and other characteristics different from those of pure RDX. It is desirable to establish the properties of such mixtures when designing new propellant formulations. Samples were aged at an elevated temperature to speed the formation of solid solutions. A least-squares analysis of X-ray diffraction data was used to obtain the lattice parameters from which unit cell volume and solubility was deduced. Both ATEC and CAB caused an expansion of the unit cell, indicating the formation of a solid solution. The limit of solubility in the ATEC/RDX mixture appeared to be approximately 13 wt% ATEC, while the CAB/RDX limit is above 16 wt% CAB. In both mixes, the cell volume expanded linearly with increasing proportion of binder.

Synthesis and crystal structure of Na3.5Cr1.5Co0.5(PO4)3 phosphate

2006 ◽  
Vol 21 (3) ◽  
pp. 210-213 ◽  
Author(s):  
Mohamed Chakir ◽  
Abdelaziz El Jazouli ◽  
Jean-Pierre Chaminade
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
X Ray ◽  
Hexagonal Unit Cell ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

A new Nasicon phosphates series [Na3+xCr2−xCox(PO4)3(0⩽x⩽1)] was synthesized by a coprecipitation method and structurally characterized by powder X-ray diffraction. The selected compound Na3.5Cr1.5Co0.5(PO4)3 (x=0.5) crystallizes in the R3c space group with the following hexagonal unit-cell dimensions: ah=8.7285(3) Å, ch=21.580(2) Å, V=1423.8(1) Å3, and Z=6. This three-dimensional framework is built of PO4 tetrahedra and Cr∕CoO6 octahedra sharing corners. Na atoms occupy totally M(1) sites and partially M(2) sites.

The CdO–CdCl2 reaction studied by thermal analysis and X-ray diffraction: X-ray diffractogram and infrared spectrum of CdCl2•2CdO

1969 ◽  
Vol 47 (6) ◽  
pp. 1045-1050 ◽  
Author(s):  
P. Ramamurthy ◽  
E. A. Secco
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Infrared Spectrum ◽  
Band Structure ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Orthorhombic System ◽  
X Ray ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

CdO and molten CdCl2 react to form CdCl2•2CdO according to the equation:[Formula: see text]The compound CdCl2•2CdO dissociates to the oxide and chloride at 680 °C. CdO and CdCl2 form a solid solution of partial miscibility of 15% by weight of CdO.The X-ray diffractogram of CdCl2•2CdO was indexed to the orthorhombic system. The unit cell dimensions are calculated to be a = 4.38 Å, b = 11.47 Å, c = 9.93 Å with 4 molecules in the unit cell. The infrared spectrum shows a band structure of two doublets and a well-defined band in the region 370–550 cm−1.

Infrared and Raman spectra and X-ray diffraction studies of solid lead(II) carbonates

1983 ◽  
Vol 61 (3) ◽  
pp. 494-502 ◽  
Author(s):  
Murray H. Brooker ◽  
S. Sunder ◽  
Peter Taylor ◽  
Vincent J. Lopata
Keyword(s):  
Unit Cell ◽  
Spectral Features ◽  
Infrared And Raman Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Carbonate Ions ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Sodium And Potassium

Four basic lead carbonates were prepared and identified by X-ray powder diffractometry. These were hydrocerussite (Pb3(OH)2(CO3)2), plumbonacrite (Pb10O(OH)6(CO3)6), and the two adducts MOH•2PbCO3 (M = Na, K). New diffraction data are presented for the latter two compounds; they both have primitive hexagonal lattices with two formula units per unit cell. The unit cell dimensions of the sodium and potassium compounds are a = 5.273 ± 0.002 Å, c = 13.448 ± 0.005 Å and a = 5.348 ± 0.002 Å, c = 13.990 ± 0.005 Å, respectively. Six possible space groups are discussed.Raman and infrared spectra are reported for all four compounds, and compared with those of cerussite (PbCO3); assignment of the spectral features is discussed. Vibrational spectra of the two MOH adducts indicate that they are isostructural, and that the structure contains a well-defined lead sub-lattice, consistent with the X-ray data. The spectra of hydrocerussite and plumbonacrite indicate that lead is present as oxygen-bridged polymeric moieties in these solids. The carbonate ions occupy two and three independent sites in hydrocerussite and plumbonacrite, respectively.

scholarly journals Chemical Preparation, Thermal Behavior and IR Studies of the New Chromium Diphosphate Hydrate and Crystal Structure of its Corresponding Anhydrous

2021 ◽  
Vol 11 (5) ◽  
pp. 13412-13420
Keyword(s):  
Thermal Behavior ◽  
Absorption Spectrometry ◽  
Unit Cell ◽  
Ir Absorption ◽  
X Ray Diffraction ◽  
Chemical Preparation ◽  
X Ray ◽  
Ir Studies ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

Chemical preparation, thermal behavior, and IR studies are given for the diphosphate Cr4(P2O7)3.28H2O and its anhydrous form Cr4(P2O7)3. Cr4(P2O7)3.28H2O, is monoclinic P2/m with the following unit-cell dimensions : a = 16.169(1)Å, b = 9.336(5)Å, c = 9.446(4)Å, β = 124.796(5)°, and Z = 4. The total dehydration of Cr4(P2O7)3.28H2O, between 90°C and 450°C, leads to its anhydrous form, Cr4(P2O7)3. Cr4(P2O7)3 is isotopic to V4(P2O7)3, crystallizing in the orthorhombic system, space group Pmcn, Z = 4 with the following unit-cell dimensions: a = 7.25(2), b = 9.38(1)Å and c = 21.00(4)Å. Cr4(P2O7)3 is stable until its melting point at 1050°C. The thermal behavior of Cr4(P2O7)3.28H2O has been investigated and interpreted by comparison with IR absorption spectrometry and X-ray diffraction experiments.

Short-range order, thermal vibration and expansion, and other properties of pseudosymmetric and mixed crystals of small organic molecules - Mixed crystals of phenzaine and n -oxyphenazine: refinement of crystal structures

1970 ◽  
Vol 266 (1180) ◽  
pp. 593-622 ◽  
Keyword(s):  
Unit Cell ◽  
Mixed Crystals ◽  
X Ray Diffraction ◽  
Small Organic Molecules ◽  
Anisotropic Temperature ◽  
Cell Dimensions ◽  
Average Unit ◽  
Unit Cell Dimensions ◽  
Temperature Factors ◽  
Atomic Coordinates

Compositions (accurate to about 1%) of mixed crystals of phenazine (P) and N -oxyphenazine (NOP) were determined from their u.v. absorption spectra. Densities, habit and unit-cell dimensions were found at 20 °C for crystals containing respectively 0, 8, 52, 81 and 100 mole % NOP relative to P; and X-ray diffraction data (F obs ) were obtained for all these and also at — 90 °C for NOP. All are isostructural (NOP being pseudocentrosymmetric) in P2 1 / a with two molecules per average unit cell. Atomic coordinates, bond lengths and anisotropic temperature factors are listed, site-occupation factors for the oxygen atoms being used for the 8, 52 and 81 mole % compositions. A qualitative explanation, in terms of structure, is offered for the anisotropic thermal expansion of NOP.

X-RAY DIFFRACTION DATA FOR ALKALI DITHIONATES

1963 ◽  
Vol 41 (2) ◽  
pp. 219-223 ◽  
Author(s):  
D. W. Larson ◽  
A. B. VanCleave
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Dimensions ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions

X-Ray powder diffraction patterns have been recorded for the alkali dithionates and for barium and ammonium dithionate. The patterns have been indexed and unit cell dimensions determined for lithium dithionate dihydrate, sodium dithionate (anhydrous), and rubidium dithionate. Previously determined cell dimensions have been confirmed in other cases.

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