Phase diagrams for the M2MoO4–Ln2(MoO4)3–Hf(MoO4)2 systems, where M = Li–Cs, Tl and Ln = La–Lu

In this paper, the results of systematic studies of complex molybdate systems M2MoO4–Ln2(MoO4)3–Hf(MoO4)2 (M = Li–Cs, Tl; Ln = La–Lu) are presented. Subsolidus phase diagrams of ternary systems were constructed and new triple molybdates were obtained. The optimum synthesis conditions for poly- and monocrystalline form were determined. According to single-crystal data, the structure of one of the representatives of triple molybdates was determined.In this paper, the results of systematic studies of complex molybdate systems M2MoO4–Ln2(MoO4)3–Hf(MoO4)2 (M = Li–Cs, Tl; Ln = La–Lu) are presented. Subsolidus phase diagrams of ternary systems were constructed and new triple molybdates were obtained. The optimum synthesis conditions for poly- and monocrystalline form were determined. According to single-crystal data, the structure of one of the representatives of triple molybdates was determined

The crystal growth and properties of novel magnetic double molybdate RbFe5_{5}(MoO4_{4})7_{7} with mixed Fe3+^{3+}/Fe2+^{2+}states and 1D negative thermal expansion

Single crystals of new compound RbFe$_5$(MoO$_4$)$_7$ were successfully grown by the flux method, and their crystal structure was determined using the X-ray single-crystal diffraction technique. The XRD analysis showed that the compound crystallizes in the monoclinic space group P21/m, with unit cell parameters a = 6.8987(4), b = 21.2912(12) and c = 8.6833(5) Å, β = 102.1896(18)°, V = 1246.66(12) Å$^3$, Z (molecule number in the unit cell) = 2, R-factor (reliability factor) = 0.0166, and T = 293(2) K. Raman spectra were collected on the single crystal to show the local symmetry of MoO$_4$ tetrahedra, after the confirmation of crystal composition using energy dispersive X-ray spectroscopy (EDS). The polycrystalline samples were synthesized by a solid-state reaction in the Ar atmosphere; the particle size and thermal stability were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses. The compound decomposes above 1073 K in an Ar atmosphere with the formation of Fe(III) molybdate. The thermal expansion coefficient along the c direction has the value α = −1.3 ppm K$^{−1}$ over the temperature range of 298–473 K. Magnetic measurements revealed two maxima in the magnetization below 20 K, and paramagnetic behavior above 50 K with the calculated paramagnetic moment of 12.7 μB per formula unit is in good agreement with the presence of $_3$Fe$^{3+}$ and $_2$Fe$^{3+}$ in the high-spin (HS) state. The electronic structure of RbFe5(MoO4)7 is comparatively evaluated using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations

Synthesis and luminescent properties of new tungstates Ln2Zr(WO4)5 (Ln = Tb, Dy)

New polycrystalline powder samples of double Ln2Zr(WO4)5 (Ln = Dy, Tb) tungstates were synthesized using high-temperature solid-phase and sol-gel methods. The conditions of the sol-gel synthesis of tungstates were optimized. The obtained phases were characterized by the X-ray powder diffraction on the basis of the crystallographic data of similar Ln–Zr molybdates. It is found that Ln2Zr(WO4)5 (Ln = Dy, Tb) double tungstates crystallize in the orthorhombic crystal system, space group Cmc21 (Z = 4). The intensive luminescence in the green spectral region for Tb2Zr(WO4)5 and yellow spectral region for Dy2Zr(WO4)5 was shown

The crystal growth and properties of novel magnetic double molybdate RbFe₅(MoO₄)₇ with mixed Fe³⁺/Fe²⁺ states and 1D negative thermal expansion

Single crystals of new compound RbFe5(MoO4)(7) were successfully grown by the flux method, and their crystal structure was determined using the X-ray single-crystal diffraction technique. The XRD analysis showed that the compound crystallizes in the monoclinic space group P2(1)/m, with unit cell parameters a = 6.8987(4), b = 21.2912(12) and c = 8.6833(5) angstrom, beta = 102.1896(18)degrees, V = 1246.66(12) angstrom(3), Z (molecule number in the unit cell) = 2, R-factor (reliability factor) = 0.0166, and T = 293(2) K. Raman spectra were collected on the single crystal to show the local symmetry of MoO4 tetrahedra, after the confirmation of crystal composition using energy dispersive X-ray spectroscopy (EDS). The polycrystalline samples were synthesized by a solid-state reaction in the Ar atmosphere; the particle size and thermal stability were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) analyses. The compound decomposes above 1073 K in an Ar atmosphere with the formation of Fe(iii) molybdate. The thermal expansion coefficient along the c direction has the value alpha = -1.3 ppm K-1 over the temperature range of 298-473 K. Magnetic measurements revealed two maxima in the magnetization below 20 K, and paramagnetic behavior above 50 K with the calculated paramagnetic moment of 12.7 mu B per formula unit is in good agreement with the presence of 3Fe(3+) and 2Fe(2+) in the high-spin (HS) state. The electronic structure of RbFe5(MoO4)(7) is comparatively evaluated using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations

Synthesis and Spectroscopic Properties of Monoclinic α‑Eu₂(MoO₄)₃

The microcrystals of monoclinic europium molybdate, α-Eu₂(MoO₄)₃, have been fabricated by solid-state synthesis at <i>T</i> = 753–1273 K for 300 h. The crystal structure of α-Eu₂(MoO₄)₃ has been refined by the Rietveld method and was found to belong to the space group <i>C</i>2/<i>c</i> with unit cell parameters <i>a</i> = 7.5576(1), <i>b</i> = 11.4709(2), <i>c</i> = 11.5158(2) Å, and β = 109.278(1)° (<i>R</i>_B = 3.39%). About 40 narrow Raman lines have been observed in the Raman spectrum of the α-Eu₂(MoO₄)₃ powder sample. The luminescence spectra of α-Eu₂(MoO₄)₃ under excitation at 355 and 457.9 nm reveal domination of induced electric dipole transition ⁵D₀ → ⁷F₂ and the presence of ultranarrow lines at ⁵D₀ → ⁷F₀ and ⁵D₁ → ⁷F₀ transitions

Synthesis and Spectroscopic Properties of Monoclinic α‑Eu₂(MoO₄)₃

The microcrystals of monoclinic europium molybdate, α-Eu₂(MoO₄)₃, have been fabricated by solid-state synthesis at <i>T</i> = 753–1273 K for 300 h. The crystal structure of α-Eu₂(MoO₄)₃ has been refined by the Rietveld method and was found to belong to the space group <i>C</i>2/<i>c</i> with unit cell parameters <i>a</i> = 7.5576(1), <i>b</i> = 11.4709(2), <i>c</i> = 11.5158(2) Å, and β = 109.278(1)° (<i>R</i>_B = 3.39%). About 40 narrow Raman lines have been observed in the Raman spectrum of the α-Eu₂(MoO₄)₃ powder sample. The luminescence spectra of α-Eu₂(MoO₄)₃ under excitation at 355 and 457.9 nm reveal domination of induced electric dipole transition ⁵D₀ → ⁷F₂ and the presence of ultranarrow lines at ⁵D₀ → ⁷F₀ and ⁵D₁ → ⁷F₀ transitions