Li4GeO4-Li2CaGeО4 phase equilibria and Li2+xCa1-xGeO4 solid solutions.

Detailed studies of the Li4GeО4-Li2CaGeО4 system by solid-phase syntheses of various compositions from pure Li4GeО4 to pure Li2CaGeО4 in the temperature range from 25 to 1125 °C is investigated for a first time. Solid state synthesis powders are characterized by X-ray and DSC/TG methods. Concentration and temperature two-phase regions of Li4GeО4 and Li2CaGeО4 as well as two-phase regions of Li2CaGeО4 and Li2+2xCa1-xGeO4 are established. Region of pure Li2+2xCa1-xGeO4 solid solution are detected too and it structure is investigated. Being structural analog to Li2+2xZn1-xGeO4 and Li2+2xMg1-xGeO4, Li2+2xCa1-xGeO4 has own specific local environment of the metal ions. The obtained results are compared with those for Li4GeО4-Li2ZnGeО4 system and for Li2+2xZn1-xGeO4 solid solution. The differences of the phase diagrams and structural features of the solid solutions are discussed.

Spectroscopic investigations of nanosized Cr3+ doped Sc2-x Inx (WO4 )3 : A new promising laser material.

Chromium(III) doped nanosized Sc2-x Inx (WO4 )3 , (x = 0-2) solid solutions were prepared by the co-precipitation/calcination method. The obtained powders were characterized using X-ray diffraction (XRD), electron paramagnetic resonance (EPR), infrared (IR), absorption and luminescence spectra. X-ray analysis showed that the compounds are pure solid solutions with orthorhombic symmetry at x values 0 and 0.5 and with monoclinic symmetry for x values 1.0, 1.5 and 2.0. The calculated crystallite size ranged from about 20 to 110 nm, except for Sc2 (WO4 )3 characterized by considerably larger sizes. IR spectra of the solid solutions contain the characteristic vibrations of the WO4 and MeO6 , (Me = Sc, In) polyhedra, building the Sc2 (WO4 )3 and In2 (WO4 )3 structures. EPR analysis proved the presence of isolated Cr3+ ions in the crystal field with rhombic symmetry. The presence of Cr3+ in sites with weak and strong crystal field was revealed by absorption and luminescence spectra. This study demonstrates the effect of hosts crystal symmetry, particles size and doping concentration on the luminescence properties.

Structural filiations in the new complex titanates SrLiMTi4O11 (M=Cr, Fe).

Two new titanates of strontium, lithium and a 3d metal, with the composition SrLiMTi4O11 (M=Cr, Fe), have been discovered. Single crystals were obtained by spontaneous crystallization from a high-temperature solution with LiBO2 as the solvent. The structure of SrLiCrTi4O11 was refined in the orthorhombic space group Pnma (Z=4), while SrLiFeTi4O11 appeared to adopt a four-times larger orthorhombic unit cell with Pbcn (Z=16). The structures can be described by a close-packed arrangement of Sr and O atoms. The unit cell contains six ;compact planes' perpendicular to [100] in the layer sequence ABACBC [(chc)2]. Ti and Cr or Fe atoms occupy some of the interstitial octahedral sites created, whereas Li atoms are in tetrahedral sites. Depending on the synthesis conditions of SrLiCrTi4O11, the distribution of Cr and Ti atoms on the four possible crystallographic sites is not the same. Having a similar compact-planes sequence, SrLiCrTi4O11 and SrLiFeTi4O11 structures differ in the arrangement of Sr and O atoms per layer of close packing, which also induces a correlated variation in the Li-tetrahedra distribution.