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:M.Piatkowska 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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