Synthesis, Structural and Magnetic Characterization of a New Scheelite Related Compound: Eu₂Mo₃O₁₂.

Abstract

Magnetic properties D 9000Synthesis, Structural and Magnetic Characterization of a New Scheelite Related Compound: Eu2Mo3O12. -The title compound is synthesized by reaction of a stoichiometric mixture of Eu2O3 and MoO2 in air (900°C, 4 d) and characterized by powder X-ray and electron diffraction, high resolution electron microscopy and magnetic measurements. Eu2Mo3O12 crystallizes in the monoclinic space group C2/c and has a complex scheelite superstructure whose essential feature is the existence of isolated Mo tetrahedra. Each Mo atom has four oxygen neighbors at distances of 1.75-1.91 Å, whereas each Eu atom has eight oxygen neighbors at 2.43 Å. The temperature dependence of the inverse magnetic susceptibility shows that Eu2Mo3O12 behaves as a Curie-Weiss paramagnet at high temperature (160-300 K), whereas it shows Van Vleck paramagnetism in the range 100-20 K. -(BOULAHYA, K.; PARRAS, M.; GONZALEZ-CALBET*, J. M.; Eur. J. Inorg. Chem. 2005, 5, 967-970;

Identifying the Unique Properties of α-Bi2Mo3O12 for the Activation of Propene

“…21 The latter system shows no catalytic activity for 0 ≤ x ≤ 0.04, suggesting that both Bi 3+ cations and vacancies together are required for a molybdate catalyst to exhibit high catalytic activity. This hypothesis is further supported by observations that europium molybdate 31 and cerium or lanthanum molybdate, 32 which also crystallize in scheelitederived structures containing trivalent cations, but with different orderings of cation vacancies, exhibit lower catalytic activities than Bi2Mo3O12.…”

Structural Characterization and Luminescent Properties of a Red Phosphor Series: Y2−xEux(MoO4)3 (x=0.4–2.0)

“…Later, InGaN-based near ultraviolet (nUV) LED chips coated with blue-green-red color phosphors are used for producing white light with high luminescence and good color rendering index. 6,7 The most common red-emitting phosphor used in these white LEDs is the Y 2 O 2 S:Eu 31 . However, it suffers from disadvantages like low luminous efficiency compared with its counterpart blue (BaM-gAl 10 O 17 :Eu 21 ) and green (ZnS:Cu 1 ,Al 31 ) phosphors, inadequate lifetime under extended UV irradiation, etc.…”

“…However, it suffers from disadvantages like low luminous efficiency compared with its counterpart blue (BaM-gAl 10 O 17 :Eu 21 ) and green (ZnS:Cu 1 ,Al 31 ) phosphors, inadequate lifetime under extended UV irradiation, etc. 8 To overcome its low efficiency, a large amount of Y 2 O 2 S:Eu 31 had to be used in comparison with the blue and green phosphors. Therefore a lot of research effort [9][10][11][12] is directed toward finding an alternative red phosphor which is more stable and possesses comparable or better luminous efficiency.…”

“…25 A comprehensive structural study of this series was initially reported by Nassau et al 19 Most of these structures are derived from scheelite but vary in the way the cations and cation vacancies are arranged, leading to an absence of inversion symmetry for rare earth ions in the host lattice. Hydrothermally synthesized La 2 (MoO 4 ) 3 :Eu 31 and Y x Gd 2Àx (MoO 4 ) 3 :Eu 31 have yielded novel microstructures and showed strong photoluminescent characteristics, which is attributed to their special morphology. 26,27 However, only 1 or 2 mol% Eu 31 was doped and the effect of Eu 31 concentration was not studied in them.…”

“…1. The europium tri-molybdate usually adopts monoclinic (C2/c) structure below 9001C 19,31 while yttrium tri-molybdate crystallizes in orthorhombic Pba2 and/or Pbcn phase depending upon the availability of moisture during synthesis and storage. 29,32 The ionic radius of yttrium lies between the smaller lanthanides forming Pbcn structure with six coordination and those larger ones preferring higher coordination numbers.…”