Synthesis, structure, magnetic, optical and Mössbauer properties of Na2FeSn(PO4)3

The phosphate Na2FeSn(PO4)3, obtained by solid state reaction, was found to be isotypic with Na2CrTi(PO4)3, with space group R-3c and unit cell parameters a = 8.6617(2)Å, c=22.0161(7)A, V = 1430.47(5)Å3, Z=6. The structural parameters refined using Rietveld method showed that the Na+ ions occupy totally the M1 sites and partially the M2 sites and sharing faces with the [Sn/FeO6] octahedra. The presence of the unique valence of ferric iron in the reported phosphate was confirmed using UV-visible diffuse-reflectance spectroscopy, magnetic measurements and Mössbauer spectroscopy

Synthesis, crystal structure and vibrational spectra of Sr_0.5Zr₂(AsO₄)₃

Sr0.5Zr2(AsO4)3 arsenate was prepared and structurally characterized by powder X-ray diffraction and by Raman and infrared spectroscopies. Its structure, which belongs to the Nasicon-type family, was refined by the Rietveld method in the R-3 space group, from X-ray powder diffraction data. The hexagonal unit-cell parameters were determined to be ah=8.965(2)  Å, ch=23.955(6)  Å, V=1667.43(6)  Å3, and Z=6. The structure is formed by an ionic three-dimensional network of AsO4 tetrahedra and ZrO6 octahedra linked by corners with Sr2+ ions occupying half of the M1 sites in an ordered manner. Raman and infrared spectra were recorded and assignments of the stretching and bending vibrations of the AsO 3/4- tetrahedra were made. The number of the peaks observed is in good agreement with that predicted by the factor-group analysis of the R-3 space group

Preparation and characterization of phosphate glasses containing titanium and vanadium

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Crystalline and vitreous Na3.89Ca0.67Al0.23Ti0.77(PO4)3 : Synthesis, crystal structure, vibrational and UV–Visible spectra

International audienceNa3.89Ca0.67Al0.23Ti0.77(PO4)3 phosphate exists in both crystalline and vitreous forms. It has been synthesized as microcrystalline powder, single crystals and glass. The structure of the crystalline form, belonging to Nasicon family with M(1)M(2)3A2(PO4)3 formula, was solved by single crystal X-ray diffraction (Space group R32, Z = 6, ah = 8.9976(1) Å, ch = 21.8312(3) Å, R1 = 0.03, wR2 = 0.06). A Rietveld refinement was also performed. The structure is formed by a 3D network of PO4 tetrahedra and AO6 (A= Na/Ca and Al/Ti) octahedra sharing corners. One of the two positions of A sites is statistically occupied by Na+ and Ca2+, the other position is statistically occupied by Al3+ and Ti4+. The remaining sodium atoms occupy totally M(1) and partially M(2) interstitial sites. Raman and infrared spectra show for the crystalline powder, broad peaks attributed principally to monophosphate PO4 modes. The structure of the glass contains PO4 and P2O7 groups and short -Ti-O-Ti-O- chains. UV–Visible spectra consist of strong bands at high energy assigned to O-Ti and O-Al electronic charge transfers

Parameningeal rhabdomyosarcoma report of 19 cases

Parameningeal rhabdomyosarcoma. Parameningeal rhabdomyosarcomas are associated with a poor long term survival. This is due to the fact that they are aggressive tumours with early involvement of the skull base. The authors report a series of 19 cases between 1984 and 1995 with a relative proportion of children, male patients and tumours of embryonal type. Three patients were operated on and only one of them was found with tumour free margins. Systemic chemotherapy using the VAC-VAd protocol was administered in 18 patients and intrathecal chemotherapy was delivered in 5 patients with involvement of the skull base. Nine patients were irradiated with doses varying from 45 to 55 Gy. Twelve patients died from 20 days to 4 years after initial treatment; 6 were lost to follow up and only one patient is living without any evidence of disease after 11 years.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Synthesis, structure and characterisation of Fe0.50Ti2(PO4)3: A new material with Nasicon-like structure

A new iron titanyl phosphate Fe0.50Ti2(PO4)3 was synthesized by both solid-state reaction and Cu2+–Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer, magnetic susceptibility measurements and optical absorption. The crystal structure of the compound was refined, using X-ray powder diffraction data, by the Rietveld profile method; it crystallizes in the rhombohedral system, space group Click to view the MathML source, with a=8.511(1) Å and c=20.985(3) Å, V=1316.45(3) Å3 and Z=6. The structure, which is compared to that of Mn0.50Ti2(PO4)3 is built up from [TiO6] octahedra and [PO4] tetrahedra which are linked by corner sharing along the c-axis. Fe2+ cations are located in half of the antiprism MI sites and are orderly distributed with vacancies within the two possible positions of the MI sites of ..