O. D. Chimitova

Phase formation in the Rb2MoO4-Er2(MoO4)3-Hf(MoO4)2 system and the crystal structure of new triple molybdate Rb5ErHf(MoO4)6

AbstractThe subsolidus region of the Rb2MoO4-Er2(MoO4)3-Hf(MoO4)2 ternary salt system is studied using X-ray powder diffraction. A novel 5: 1: 2 triple molybdate, Rb5ErHf(MoO4)6, is found to form in the system. Crystals of Rb5ErHf(MoO4)6 are flux-grown under spontaneous nucleation conditions. The composition and crystal structure of Rb5ErHf(MoO4)6 are refined in a single-crystal X-ray diffraction experiment (X8 APEX diffractometer, MoKα radiation, 1753 reflections, R = 0.0183). The crystals are trigonal; a = 10.7511(1) Å, c = 38.6543(7) Å, V = 3869.31(9) Å3, dcalc = 4.462 g/cm3, Z = 6, space group % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuaiqaio% dagaqeaiaadogaaaa!3881!

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

R\bar 3c

Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M = Li, Na, or Rb)

. The mixed three-dimensional framework of the structure is formed of MoO4 tetrahedra, each sharing corners with two ErO6 and HfO6 octahedra. Two types of Rb atoms occupy large cavities of the framework. The distribution of the Er3+ and Hf4+ cation over two positions is refined in the course of structure solution.

Synthesis, crystal structure, and electrical properties of the new ternary molybdate Rb5NdHf(MoO4)6

Triple molybdates of the compositions Rb5LnHf(MoO4)6 (5:1:2) and Rb2LnHf2(MoO4)6.5 (2:1:4), Ln = Ce-Lu, were prepared by solid-phase reactions. The temperature dependence of the electrical conductivity of the compounds Rb5LnHf(MoO4)6 (5:1:2) at 200–500°C was studied.

CRYSTAL STRUCTURE OF A NEW TERNARY MOLYBDATE Rb5CeZr(MoO4)6

The systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO4)2, which is formed in the Rb2MoO4-Fe2(MoO4)3 system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoKα radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) Å3, Z = 1, ρcalc = 3.670 g/cm3, space group R3m1. The structure is formed by layers of FeO6 octahedra sharing corners with MoO4 tetrahedra and RbO12 icosahedra.

Synthesis, structural and vibrational properties of microcrystalline β-RbSm(MoO4)2

Systems Tl2MoO4-E(MoO4)2 (E = Zr, Hf) are studied using X-ray powder diffraction, DTA, and IR spectroscopy. Compounds Tl8E(MoO4)6 and Tl2E(MoO4)2 are found in these systems. T-x diagrams for the Tl2MoO4-Zr(MoO4)2 system are designed. Single crystals are grown and structure is solved for Tl8Hf(MoO4)6. The compound crystallizes in a monoclinic structure with the unit cell parameters a = 9.9688(6) Å, b = 18.830(1) Å, c = 7.8488(5) Å, β = 108.538(1)°, Z = 2, space group C2/m. The main structural fragment is a [HfMo6O24]8− isle group. Three crystallographically independent types of Tl polyhedra uniformly fill spaces between [HfMo6O24]8− fragments to form a three-dimensional framework.

Crystal structure of a new ternary molybdate in the Rb2MoO4-Eu2(MoO4)3-Hf(MoO4)2 system

Phase equilibria in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M = Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb2MoO4-Cr2(MoO4)3-Zr(MoO4)2 system with the molar ratios of the starting components equal to 5: 1: 1 (S2) and 1: 1: 1 (S1). Proceeding from that the isostructurality of Rb5FeHf(MoO4)6 and S2 the unit cell, parameters are determined for S2.

Crystal structure of triple molybdate in the Rb2MoO4—Nd2(MoO4)3—Zr(MoO4)2 system

The subsolidus phase relations in the ternary salt system Rb2MoO4-Nd2(MoO4)3-Hf(MoO4)2 were studied by X-ray powder diffraction. The ternary molybdates Rb5NdHf(MoO4)6 (1) and Rb2NdHf2(MoO4)6.5 are formed in this system. Compound 1 without impurities was synthesized by the solid-phase method by varying the temperature in the range of 400–600 °C and the annealing time from 70 to 110 h. Single crystals of compound 1 were grown by the flux method. The structure of compound 1 was established and the electrical properties of ceramic samples of this compound were investigated. This ternary molybdate has mixed electronic-ionic conductivity with the ionic component predominating at 200–500 °C.