RESUMO
In this work, using techniques of X-ray diffraction and Raman spectroscopy, we report the composition and high-temperature induced phase transition in the system LiZnV1-xAsxO4 (0⩽x⩽1). Both techniques showed that the increase of arsenic amount induced a structural transition from R-3 LiZnVO4 type to LiZnAsO4 type belonging to R3 space group, the transition occurring between x=0.7 and x=0.8. Furthermore, increasing temperature for the compositions (0.8⩽x⩽1) manifests a transition from the LiZnAsO4 structural type with R3 space group to the R-3 LiZnVO4 structural type. For this series, the transition from the space group R3 to the centro-symmetric space group R-3 shows considerable changes in the compositional and temperature dependencies of the bands: spectral positions of all the observed Raman bands exhibit shifts linearly proportional to the temperature increase, with points of shift-rate changes revealing a symmetry change. The Raman-spectra based temperature-composition phase diagram confirms the results obtained using the method of Rietveld refinements, thus showing the R-3 to R3 transition occurring between x=0.7 and 0.8.
RESUMO
The salt diaquo-diammine-bis(3,4'-bi-1,2,4-triazolate) copper(II) of the formula [Cu(bTA-)2(NH3)2(H2O)2] has been synthesized and structurally characterized by X-ray single crystal diffraction analysis. This complex adopts a monomeric structure. This monomer crystallizes in the triclinic system, space group P1 with a=5.9657 Å; b=6.8975 Å; c=9.9892 Å; α=106.181°; ß=97.868°; γ=90.800° and Z=1. The Cu atom is coordinated by two nitrogen atoms of two monodentate bitriazolate ligands, two nitrogen atoms of NH3 and two water molecules in a distorted octahedral geometry. The complex has been also characterized by elemental analysis and studied by electronic and vibrational spectroscopy. The obtained results are in good agreement with the structure determined by X-ray diffraction analysis.
