Stnthesis and polymorphism of crystals of rubidium-lanthanum tungstate RbLa(WO/sub 4/)/sub 2/
Single crystals of RbLa(WO/sub 4/)/sub 2/ in three modifications have been prepared by crystallization from solution in the melt under spontaneous nucleation conditions, viz., isostructural with monoclinic KY(WO/sub 4/)/sub 2/ KNd(WO/sub 4/)/sub 2/, and sheet-layered having the structure of orthorhombic KY(MO/sub 4/)/sub 2/. The crystals of the last two phases, as shown by differential thermal analysis and x-ray diffraction investigations, are metastable (..beta.. and ..gamma.. modifications). It has been found that the compounds may crystallize in five polymorphic modifications. From high-temperature powder diffraction data (>800 degreeC) the high-temperature modification (delta) has been assigned to an unknown structural type which on rapid cooling is converted into a modification (delta') having the structure of pseudo-tetragonal RbPr(MoO/sub 4/)/sub 2/. Single crystals of the ..cap alpha.. and ..beta.. phases are analogous in their modes of growth and habit and exhibit an affinity with crystals of tetragonal scheelite. The crystal structure of ..beta..-RbLa(WO/sub 4/)/sub 2/ has been refined by x-ray structural analysis, and a comparative crystal chemical analysis of it with the structure of the ..cap alpha..-modification has been carried out. (AIP)
- Research Organization:
- Institute of Inorganic Chemistry, Siberian Branch of the Academy of Sciences of the USSR
- OSTI ID:
- 7267407
- Journal Information:
- Sov. Phys. - Crystallogr. (Engl. Transl.); (United States), Journal Name: Sov. Phys. - Crystallogr. (Engl. Transl.); (United States) Vol. 21:1; ISSN SPHCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360602* -- Other Materials-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
CHEMICAL PREPARATION
COHERENT SCATTERING
CRYSTAL GROWTH
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CRYSTALLIZATION
CRYSTALS
DIFFERENTIAL THERMAL ANALYSIS
DIFFRACTION
LANTHANUM COMPOUNDS
MONOCLINIC LATTICES
MONOCRYSTALS
NUCLEATION
PHASE TRANSFORMATIONS
RARE EARTH COMPOUNDS
RUBIDIUM COMPOUNDS
SCATTERING
SYNTHESIS
THERMAL ANALYSIS
TUNGSTATES
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION