Structural, morphological and optical properties of new Eu-doped and vacancied lead molybdato-tungstates
来源期刊：Journal of Rare Earths2018年第6期
论文作者：李超 E.Tomaszewicz
文章页码：635 - 641
摘 要：A new tetragonal,scheelite-type Pb1-3 x■xEU2 x（MoO4）1-3 x（WO4）3 x（0< x ≤0.1970 and ■ denotes A-site vacancies） solid solution was synthesized via solid state reaction method. The X-ray diffraction（XRD） and scanning electron microscopy（SEM） results confirm the formation of single, tetragonal scheelite-type phases（space group I41/a） with the average crystallite size in the range of ～20-100 μm. Substitution of Pb2+ with Eu3+ is relatively easy despite the large difference in ionic radii, and the formation of vacancies is necessary to compensate the excess positive charge in PbMoO4 framework. A change in lattice parameters（both a and c as well as lattice parameter ratio c/a） and progressive deformation of MoO4 and WO4 tetrahedra with increasing Eu concentration are observed. Thermal stability of Eu-doped materials strongly depends on the concentration of Eu3+ ions. The Pb1-3 x■xEu2 x（MoO4）1-3 x（WO4）3 x solid solution for x=0.0098 shows the highest melting point（1057 ℃） which is slightly higher than that of pure PbMoO4（1040 ℃）. The UV-vis diffuse reflectance spectroscopy（DRS） and the Tauc plots were used to extrapolate the optical indirect band gap（Eg） of doped materials. Eu-doped ceramics are insulators（Eg > 3 eV） and their band gap nonlinearly decreases with increasing dopant concentration.
M.Piatkowska，E.Tomaszewicz
Faculty of Chemical Technology and Engineering,Department of Inorganic and Analytical Chemistry,West Pomeranian University of Technology,Szczecin
摘 要：A new tetragonal,scheelite-type Pb1-3 x■xEU2 x（MoO4）1-3 x（WO4）3 x（0< x ≤0.1970 and ■ denotes A-site vacancies） solid solution was synthesized via solid state reaction method. The X-ray diffraction（XRD） and scanning electron microscopy（SEM） results confirm the formation of single, tetragonal scheelite-type phases（space group I41/a） with the average crystallite size in the range of ～20-100 μm. Substitution of Pb2+ with Eu3+ is relatively easy despite the large difference in ionic radii, and the formation of vacancies is necessary to compensate the excess positive charge in PbMoO4 framework. A change in lattice parameters（both a and c as well as lattice parameter ratio c/a） and progressive deformation of MoO4 and WO4 tetrahedra with increasing Eu concentration are observed. Thermal stability of Eu-doped materials strongly depends on the concentration of Eu3+ ions. The Pb1-3 x■xEu2 x（MoO4）1-3 x（WO4）3 x solid solution for x=0.0098 shows the highest melting point（1057 ℃） which is slightly higher than that of pure PbMoO4（1040 ℃）. The UV-vis diffuse reflectance spectroscopy（DRS） and the Tauc plots were used to extrapolate the optical indirect band gap（Eg） of doped materials. Eu-doped ceramics are insulators（Eg > 3 eV） and their band gap nonlinearly decreases with increasing dopant concentration.
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