Hydrothermal synthesis and structural characterization of several complex rare earth tantalates: LnTaO(OH) (Ln = La, Pr) and LnTaO(OH) (Ln = Pr, Nd).

Reactions are reported of early rare earth oxides, REO (RE = La, Pr, Nd) with TaO under hydrothermal conditions (650 °C, 1.5 kbar) in concentrated aqueous hydroxide (20-30 M KOH) as a mineralizer. Under various stoichiometries several members of two new structure types were isolated, LnTaO(OH) (Ln = La, Pr) and LnTaO(OH) (Ln = Pr, Nd).

High temperature hydrothermal synthesis of rare-earth titanates: synthesis and structure of RETiO(OH) (RE = La, Er), SmTiO(OH), RETiO(OH) (RE = Tm-Lu) and CeTiO.

Reactions of rare-earth oxides with TiO2 were performed in high temperature (650-700 °C) hydrothermal fluids. Two different mineralizer fluids were examined, 20 M KOH and 30 M CsF, and their respective products analyzed. When concentrated KOH fluids were used, single crystals of a variety of new OH- containing species were isolated and structurally characterized: RE5Ti4O15(OH) (RE = La, Er) I, Sm3TiO5(OH)3II and RE5Ti2O11(OH) (RE = Tm-Lu) III.

Investigation of a Structural Phase Transition and Magnetic Structure of NaBaFe(VO): A Triangular Magnetic Lattice with a Ferromagnetic Ground State.

The structural and magnetic properties of a glaserite-type NaBaFe(VO) compound, featuring a triangular magnetic lattice of Fe (S = 2), are reported. Temperature dependent X-ray single crystal studies indicate that at room temperature the system adopts a trigonal P3̅m1 structure and undergoes a structural phase transition to a C2/c monoclinic phase slightly below room temperature (T = 288 K). This structural transition involves a tilting of Fe-O-V bond angles and strongly influences the magnetic correlation within the Fe triangular lattice.

Crystal chemistry and the role of ionic radius in rare earth tetrasilicates: BaRESiOF (RE = Er-Lu) and BaRESiO (RE = La-Ho).

Structural variations across a series of barium rare earth (RE) tetrasilicates are studied. Two different formulas are observed, namely those of a new cyclo-silicate fluoride, BaRESiOF (RE = Er-Lu) and new compounds in the BaRESiO (RE = La-Ho) family, covering the whole range of ionic radii for the rare earth ions. The BaRESiO series is further subdivided into two polymorphs, also showing a dependence on rare earth ionic radius (space group P{\overline 1} for La-Nd, and space group C2/c for Sm-Ho).

One-Pot Hydrothermal Synthesis of Tb(GeO)O(OH) and KTbGeO: Preparation of a Stable Terbium(4+) Complex.

Two terbium germanates have been synthesized via high-temperature and high-pressure hydrothermal synthesis with 20 M KOH as a mineralizer using TbO as a starting material. Tb(GeO)O(OH) crystallizes in trigonal space group R3̅, is built up of isolated GeO units, and contains a complex arrangement of terbium oxide polyhedra. KTbGeO is a terbium(4+) pyrogermanate that is isostructural with KZrGeO and displays a rare stable Tb oxidation state in the solid state.

Crystal chemistry of hydrothermally grown ternary alkali rare earth fluorides.

The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La-Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered.