Synthesis of rare earth antimonate pyrochlores and cathodoluminescence of europium(3+) in 3Gd2O3.Sb2O5

Nath, Debojyoti

doi:10.1021/ic50094a019

Cited by 30 publications

(11 citation statements)

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“…In addition, the low-temperature forms of La,SbO, and Pr3-SbO, have been stated to transform to "highly distorted P" structures on heating at 1 4005/60 h and 1450' /78 h respectively; neither the low nor the high-temperature structures are of the W or thortveitite types (64). However, the spacings and intensities reported for the powder diffraction patterns of these high-temperature forms (64) show strong similarities to those given by Savchenko et al (65) for Ln,NbO, (Ln = La. Ce, Pr).…”

Section: P0/yt7701/1/7 A/iel't7~tilie~mentioning

confidence: 99%

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Brisse¹,

Stewart²,

Seidl³

et al. 1972

Can. J. Chem.

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The cubic pyrochlores Cd,Nb,O,, Cd2Ta,0,. S n 2 N b 2 0 j . S n z T a 2 0 7 . Cd,Sb20,, Ca2Sb,0,, M n 2 S b 2 0 i , PbzSb,O,. and related compounds were prepared and investigated by a number of methods. On heating above 700'. Ca,SbzO,(pyrochlorc) transformed to Ca,Sb,O,(weberitej, while Pb,Sb201(pyrochlore) changed to a rhombohedrally distorted P b 2 S b 2 0 j pyrochlore. Refinement of the crystal structures of Cd,Nb,O, and C d z T a 2 0 , from powderdiffractometer intensities yielded 0.434(2) and 0.434(3) respectively as the best estimates of .\. (O,). Specimens of natural bindheimite and stibiconite were also examined. Stibiconite from San Luis Potosi (Mexico) was shown. on the evidence of its Mossbauer "'Sb spectrum, to contain Sb(V) and Sb(II1) in the approximate ratio of 0.2.BaCd,CI,.5HI0 and BaCd2CI,.2H20 both give powder diffraction patterns of the pyrochlore type. The chlorine could be partially replaced by Br to give mixed crystals BaCd,CI,-,Brl,5H,0 almost up to z = 2.The crystal chemistry of 2-5 oxide pyrochlores and the relationship of the weberite to the pyrochlore phases are discussed. On discute d e la cristallochiniie des pyrochlores oxygknes de type 2-5 ainsi que de la relation entrc les phases pyrochlore et wdberite. Canadian Journal of Chemistry. 50, 3648 (1972) As a sequel to our previous investigations of oxide pyrochlores of compositions A;+B;+O, ( 3 -4 pyrochlores) and Ai+B:+O, ( 1 -5 pyrochlores) (IPS), some corresponding 2-5 pyrochlores have been studied. Minerals of this type (pyrochlore. niicrolite etc.) have been known for a long time. and the discovery of ferroelectricity in Cd2Nb20, (9) initiated a search for similar compounds with unusual dielectric properties. This search has proved disappointing in that it has uncovered but a minuscule number of new ferroelectrics of this structure type. It showed, however, that for some combinations of divalent and pentavalent cations the composition of the pyrochlore (P) phase is not limited to the ideal A,B,O, stoichiometry, while for other combinations oiz!v hypostoichiometric P phases can be prepared by conventional methods. The 2-5 pyrochlores are then best described by the general formula A , + = B 2 0 6 +,. The range of z is determined by the particular combination of A and B. and may include unity. The stability of the P structure can be correlated, for 3-4 pyrochlores, with the ionic size and radius ratio of the cations (10). A similar correlation is less satisfactorv for the 2--5 pyrochlores ( 1 1). Pentavalent cations of suitable size and chemistry are relatively few, and the absence, among divalent elements. of an extensive sequence of closely related ions, such as that formed by the trivalent lanthanons, makes each of the 2-5 P phases more unique. The Can. J. Chem. Downloaded from www.nrcresearchpress.com by 34.208.6.16 on 05/10/18For personal use only.

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Section: P0/yt7701/1/7 A/iel't7~tilie~mentioning

confidence: 99%

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Brisse¹,

Stewart²,

Seidl³

et al. 1972

Can. J. Chem.

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“…5. The equilibrium oxygen partial pressure of reaction (2) shown in the figure has been reported previously by the authors. 12 Assuming that Eu 2 Mn 4/3 W 2/3 O 7 has stoichiometric form, the standard Gibbs free energy changes of reactions (3) and (4) are calculated from the data in Table I (11) and that of reaction (7) was also determined by the cell, Fe, Fe x Oj11 2 CSZjEr 2 Mn 4/3 W 2/3 O 7 , Er 2 MnWO 7 , Er 6 MnO 12 , MnO .…”

Section: B Equilibrium Oxygen Partial Pressures and Standard Gibbs Fmentioning

confidence: 53%

“…Most of these compounds have the pyrochlore structure with a cubic cell [1][2][3][4][5][6][7] and some of the compounds have the distorted pyrochlore structure with a rhombohedral (or hexagonal) cell. [8][9][10] In the Ln-Mn -W-O system, Ln 2 Mn 4/3 W 2/3 O 7 (Ln Sm-Lu and Y) were first synthesized by Bazuev et al 11 They reported that the powder x-ray diffraction patterns of those compounds could be indexed by hexagonal symmetry, and also reported the magnetic susceptibility of Y 2 Mn 4/3 W 2/3 O 7 .…”

Section: Introductionmentioning

confidence: 99%

Decomposition behavior of Ln₂Mn_4/3W_2/3O₇ (Ln = Eu and Er) in reducing atmosphere and their thermodynamic properties

Atsumi

Kamegashira

1997

J. Mater. Res.

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Decomposition behavior of Ln2Mn4/3W2/3O7 (Ln = Eu and Er) in reducing atmosphere at 1273 K was determined. These compounds decomposed to LnMnO3 and Ln2MnWO7 at PO2 = 10−8.46 atm for Ln = Eu and 10−7.46 atmosphere for Ln = Er, respectively. Decomposition product Eu2MnWO7 decomposed to Eu2MnWO6 at PO2 = 10−15.67 atm, while Er2MnWO7 decomposed to Er2O3, MnO, and W less than 10−17 atm. The standard Gibbs free energy changes of decomposition for Eu2Mn4/3W2/3O7, Eu2MnWO7, and Er2Mn4/3W2/3O7 at 1273 K were determined to be 34.4 kJ · mol−1, 191.9 kJ · mol−1, and 44.8 kJ · mol−1, respectively. The standard Gibbs free energy changes of formation of Er2Mn4/3W2/3O7 and Er2MnWO7 were also determined to be −2429.5 and −2463.2 kJ · mol−1 at 1273 K, respectively.

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“…Figure 1 shows the magnetic-dipole ( 5 D1) -_7F 1 ) and electric-dipole (D. --7F 0 , 5 D 0 -__) 7F 2 , 5 D, --7F 4 ) transitions for cubic pyrochlore for the samples that contain Sn, Ti, and Zr. Assignments were made based on those by Nath 9 …”

Section: Particle Size Distribution and Optical Bandgapmentioning

confidence: 99%

“…Y,. 9 Eu 06 40 3 exhibits a luminance of 25 fL at 300 V. The luminous efficiency is 0.02 lm/W. To compete with liquid crystal displays, an efficiency of 2 to 3 lm/W is required for a red phosphor.…”

Section: Cathodoluminescence Propertiesmentioning

confidence: 99%

Low-Voltage Cathodoluminescent Properties of Europium-Activated Anion-Deficient Fluorites

1994

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We have examined the optical bandgap, particle size distribution, photoluminescence spectra, and cathodoluminescent response of fifteen phosphors that contain transition-metal and main-group sensitizers. We determined luminance versus applied voltage curves for electron energies from 5 to 1000 eV. Seven phosphors exhibit threshold voltages less than 110 V. Y1. 96 Eu 0 . 04 0 3 exhibits a threshold voltage of 13 V and, at 300 V, displays a luminance of 25 fL and a luminous efficiency of 0.02 lm/W.

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Synthesis of rare earth antimonate pyrochlores and cathodoluminescence of europium(3+) in 3Gd2O3.Sb2O5

Cited by 30 publications

References 0 publications

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Decomposition behavior of Ln₂Mn_4/3W_2/3O₇ (Ln = Eu and Er) in reducing atmosphere and their thermodynamic properties

Low-Voltage Cathodoluminescent Properties of Europium-Activated Anion-Deficient Fluorites

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Synthesis of rare earth antimonate pyrochlores and cathodoluminescence of europium(3+) in 3Gd2O3.Sb2O5

Cited by 30 publications

References 0 publications

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Pyrochlores. VIII. Studies of some 2–5 Pyrochlores and Related Compounds and Minerals

Decomposition behavior of Ln2Mn4/3W2/3O7 (Ln = Eu and Er) in reducing atmosphere and their thermodynamic properties

Low-Voltage Cathodoluminescent Properties of Europium-Activated Anion-Deficient Fluorites

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Decomposition behavior of Ln₂Mn_4/3W_2/3O₇ (Ln = Eu and Er) in reducing atmosphere and their thermodynamic properties