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The novel vanadium oxides Rb2CaV2O7 and Cs2CaV2O7 have been prepared by solid-state reaction and their crystal structures determined and refined using X-ray, neutron powder and electron diffraction data. Rb2CaV2O7 and Cs2CaV2O7 are isostructural, crystallizing in space group P21/n with unit cell parameters: a = 13.8780(1), b = 5.96394(5), c = 10.3376(1) Å, ? = 104.960(1)º and a = 14.0713(2), b = 6.0934(1), c = 10.5944(1) Å, ? = 104.608(1)º, respectively. Their crystal structures can be described as a framework of CaO6 octahedra and V2O7 pyrogroups with alkaline metals found in the tunnels formed. Photoluminescence (PL) and PL excitation spectra of the concerned pyrovanadates have been studied in the vacuum ultraviolet (VUV) to visible light (VIS) range as well as their pulse cathode luminescence (PCL) spectra and the kinetic parameters of PCL. In the PL and the PCL spectra of both pyrovanadates recorded at T = 300 K a broad band with maxima at 2.38, 2.2 eV and a shoulder (band) at 2.08 eV have been observed. At T = 10 K the band at 2.08 eV becomes the main band in the spectra. Two types of luminescence centers for each pyrovanadates, with very similar excitation bands at 3.75, 4.84, 6.2, 7.3 and 9.1 eV, have been found. The nature of the luminescence centers connected with the band 2.08 eV (center I) and the bands 2.2 and 2.38 eV (center II) is discussed, övrigt antal författare 7st.

Powder samples of the reduced oxoniobates Eu0.7NbO3, EuNbO3, Eu2Nb5O9, EuNb8O14 and BaNb8O14 have been synthesised. EuNbO3 and Eu0.7NbO3 adopt the perovskite type structure (space group Pm3m) with unit cell parameters a = 4.021 (1) and 3.981 (3) Angstrom, respectively. Eu,Nb,Og exhibits an intergrowth structure which can be described as alternating slabs of NbO and EuNbO3. It crystallises in P4/mmm with a = 4.131(1) and c = 12.043(5) Angstrom. EuNb8O14 and the here synthesised modification of BaNb8O14 is isostructural with SrNb8O14. The structures of EuNb8O14 and BaNb8O14 have been refined from X-ray powder diffraction data with the Rietveld technique, They have the unit cell parameters a = 9.2272(1), b = 10.2647(2), c = 5.9381(1) and a = 9.3451(1), b = 10.2689(2), c = 5.9470(4) Angstrom, (space group Pbam), respectively. In all the studied compounds AO(12) cuboctahedra (A = Eu, Ba) form either chains (in ANb(8)O(14)), double layers (in Eu2Nb5O9) or three-dimensional nets (in EuNbO3 and Eu0.7NbO3). Magnetic susceptibility measurements show temperature independent paramagnetism for BaNb8O14, while the susceptibilities of the Eu niobates follow Curie-Weiss laws with effective magnetic moments in good agreement with the expected mu(eff)=7.9 mu(B) for EU(2+). Eu0.7NbO3 and Eu1.0NbO3 exhibit ferromagnetic ordering below 4 K. BaNb8O14 and EuNb8O14 are semiconductors, while Eu2Nb5O9, EuNbO3 and Eu0.7NbO3 are metallic.

Ba3Nb16O23 was prepared by reducing a mixture of BaCO3 and Nb2O5 with acetylene soot under vacuum at 1550-1600-degrees-C. The structure was determined from high resolution electron microscopy images and was refined by the Rietveld technique using X-ray and neutron powder diffraction data. The unit cell parameters are a = 20.9301(4) angstrom, b = 12.4785(3) angstrom and c = 4.1619(1) angstrom, space group Cmmm, Z = 2. The crystal structure can be described as an intergrowth of BaNbO3 and NbO. Characteristic building units are quadruple chains of corner-sharing Nb6 octahedra connected via columns with a perovskite-type structure to form a three-dimensional network.