Studies on some ternary oxyborates of the Na{sub 2}O-Me{sub 2}O{sub 3}-B{sub 2}O{sub 3} (Me=rare earth or aluminum) systems: Synthesis, structure and crystal growth
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Building 11, 1113 Sofia (Bulgaria)
- Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB), CNRS (UPR 9048), Universite Bordeaux 1, 87 avenue du Docteur A. Schweitzer, 33608 Pessac (France)
Sodium rare-earth oxyborates Na{sub 2}RE{sub 2}O(BO{sub 3}){sub 2} (RE=Y, Nd, Er) were prepared for the first time in the present study. They were found to be isostructural with phases of the same composition containing Sm, Eu or Gd and reported by Corbel et al. [J. Solid State Chem.144 (1999) 35-44]. It was shown that the yttrium and erbium compounds could be synthesized at 900-1000deg. C by a solid-state reaction between oxides in an equimolecular ratio. With both oxyborates melting led to decomposition into a mixture of Y(Er)BO{sub 3}, Y{sub 2}(Er{sub 2})O{sub 3} and Na{sub 2}B{sub 4}O{sub 7}. Just the opposite was observed during thermal treatment of the oxide mixture containing Nd{sub 2}O{sub 3}, from which a practically pure phase of Na{sub 2}Nd{sub 2}O(BO{sub 3}){sub 2} was only obtained after melting. The attempts to synthesize the oxyborate Na{sub 2}La{sub 2}O(BO{sub 3}){sub 2} showed it to be unstable, this leading to the formation of a mixture containing, in addition to Na{sub 2}La{sub 2}O(BO{sub 3}){sub 2}, also other already known stable phases of the system Na{sub 2}O-La{sub 2}O{sub 3}-B{sub 2}O{sub 3} along with an unknown ternary oxide phase. This phase was found to represent a new oxyborate of sodium and lanthanum with the formula Na{sub 3}La{sub 9}O{sub 3}(BO{sub 3}){sub 8}, whose single crystals were obtained by flux growth. It was established that synthesis of a polycrystalline material with the same composition was also possible using solid-state interaction between Na{sub 2}CO{sub 3}, La{sub 2}O{sub 3} and H{sub 3}BO{sub 3} at 1000-1100 deg. C. X-ray diffraction experiments on single crystals were used to solve the structure of Na{sub 3}La{sub 9}O{sub 3}(BO{sub 3}){sub 8}. The unit cell was found to be hexagonal, space group P62m (No. 189) with Z=1. The compound can be regarded as the forefather of a second group of oxyborates representing a new family of isostructural compounds, Na{sub 3}RE{sub 9}O{sub 3}(BO{sub 3}){sub 8}. Such phases were obtained with RE=Nd, Sm and Eu whereas with RE=Y and Gd, the synthesis experiments failed. The concentration and temperature regions of crystallization of the double-oxyborate Na{sub 2}Al{sub 2}O(BO{sub 3}){sub 2} in the ternary system Na{sub 2}O-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} were determined. This compound was shown to melt incongruently at 970+/-3 deg. C, which made high-temperature solution growth most appropriate for obtaining its single crystals with NaBO{sub 2} as the best solvent. On the basis of the data obtained, a composition of the initial solution was proposed, the validity of the choice being demonstrated by the growth of Na{sub 2}Al{sub 2}O(BO{sub 3}){sub 2} single crystals on a seed using the top-seeded solution growth (TSSG) technique and slow cooling of the solution.
- OSTI ID:
- 20905447
- Journal Information:
- Journal of Solid State Chemistry, Vol. 179, Issue 9; Conference: 15. international symposium on boron, borides and related compounds, Hamburg (Germany), 21-26 Aug 2005; Other Information: DOI: 10.1016/j.jssc.2006.01.027; PII: S0022-4596(06)00031-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Syntheses, crystal structures, and optical properties of Pb{sub 6}B{sub 3}O{sub 10}X (X=F, Cl, Br)
Tuning the melting point and phase stability of rare-earth oxides to facilitate their crystal growth from the melt
Related Subjects
ALUMINIUM OXIDES
BORATES
BORIC ACID
BORON OXIDES
CRYSTAL GROWTH
HEAT TREATMENTS
HEXAGONAL LATTICES
LANTHANUM OXIDES
MONOCRYSTALS
NEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SODIUM CARBONATES
SODIUM COMPOUNDS
SODIUM OXIDES
SPACE GROUPS
SYNTHESIS
TEMPERATURE RANGE 1000-4000 K
X-RAY DIFFRACTION