B. G. Bazarov

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!

A NEW TYPE OF MIXED FRAMEWORK IN THE CRYSTAL STRUCTURE OF BINARY MOLYBDATE Nd2Zr3(MoO4)9

R\bar 3c

Phase equilibria in the Tl2MoO4-Nd2(MoO4)3-Hf(MoO4)2 system and the crystal structure of double molybdate TlNd(MoO4)2

. 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.

Phase equilibria in the system Li2O-MgO-B2O3

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.

Synthesis and electrical properties of triple molybdates

Single crystals of binary molybdate Nd2ZrMoO4)9 were grown. The crystal structure of this compound was investigated by X-ray diffraction analysis (CAD-4 diffractometer, MoKα radiation, 2844 reflections. R = 0.0230), and a new type of structure was found. The crystals are trigonal with cell dimensions a = 9.804(1), c = 58.467(12) å, V= 4867(1) å3, Z = 6, dcalc = 4.098 g/cm3, space group R3−c. The structure involves polyhedra of three types: MoO4 tetrahedra, ZrO6 octahedra, and NdO9 tricapped trigonal prisms linked by their common vertices into an original three-dimensional framework.

Systems Tl2MoO4-E(MoO4)2, where E = Zr or Hf, and the crystal structure of Tl8Hf(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.

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

The Tl2MoO4-Nd2(MoO4)3-Hf(MoO4)2 system was studied in the subsolidus region using X-ray powder diffraction. New triple molybdates were found to exist in this system: Tl5NdHf(MoO4)6 (5: 1: 2), TlNdHf0.5(MoO4)3 (1: 1: 1), and Tl2NdHf2(MoO4)6.5 (2: 1: 4). The first TlNd(MoO4)2 single crystals were grown from melt solutions with spontaneous nucleation. Their crystal structure was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoKα radiation, 386 F(hkl), R = 0.0136). The tetragonal unit cell parameters are as follows: a = 6.3000(2) Å, c = 9.5188(5) Å, V = 377.80(3) Å3, Z = 2, ρcalcd = 5.876 g/cm3, space group P4/nnc. The structure is a framework built of NdO8 and TlO8 tetragonal antiprisms linked via shared lateral edges and alternating in the checkerboard order. Layers share oxygen vertices with MoO4 interlayer tetrahedra and are linked into the framework.

Subsolidus phase diagrams of the systems Cs2MoO4-R2(MoO4)3-Zr(MoO4)2, where R = Al, Sc, or In

The subsolidus region of the Li2O-MgO-B2O3 system has been studied by X-ray powder diffraction and differential thermal analysis. Isothermal sections at 500–550 and 650–700°C have been designed. The following complex borates have been found to form: at 500–550°C, Li2MgB2O5 and LiMgBO3 are formed; at 650–700°C, a new phase Li4MgB2O5 is formed along with LiMgBO3; and at 5500–600°, Li2MgB2O5 is formed.