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Solid solutions of Sr 9+x Ni 1.5-x (PO 4 ) 7 that are structurally related to β-Ca 3 (PO 4 ) 2 are formed in the compositional range of 0.14 e x e 0.39. We investigated static disorder in Sr 9.3 Ni 1.2 -(PO 4 ) 7 (x ) 0.3, space group: R3 hm) by X-ray and neutron powder diffraction. The electrondensity distribution in Sr 9.3 Ni 1.2 (PO 4 ) 7 was determined by Rietveld refinement and subsequent whole-pattern fitting based on the maximum entropy method (MEM) from synchrotron X-ray powder diffraction data measured at 100 K. The resulting electron densities served to derive an expedient split-atom model. By adopting this model, we refined the structure parameters of Sr 9.3 Ni 1.2 (PO 4 ) 7 by the Rietveld method from the X-ray diffraction data as well as from time-of-flight neutron powder diffraction data measured at 293 K. The Rietveld refinement with the X-ray diffraction data gave R wp ) 5.39% and R B ) 2.80%. Further MEM-based pattern fitting appreciably decreased the R factors to R wp ) 5.18% and R B ) 1.03%, which demonstrates that the highly disordered structure of Sr 9.3 Ni 1.2 (PO 4 ) 7 can be expressed more accurately with electron densities than with structure parameters. The asymmetric unit of Sr 9.3 Ni 1.2 (PO 4 ) 7 contains two Sr sites (Sr1 and Sr3), one Ni site (Ni5), one mixed-metal site (M4), two P sites (P1 and P2), and five O sites. Sr3 atoms are statistically distributed among four positions near the center of symmetry. Sr 2+ and Ni 2+ ions are split to occupy the M4 site that is 75% vacant. P1O 4 tetrahedra are orientationally disordered.

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In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can-1CunO2n+2+ (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+ and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

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In the present work, an electrochemically driven ceramic oxygen generator (ECOG) device is investigated. The present device is based on an electrode supported architecture. Structural and electrochemical characterizations of the electrochemical cell have been carried out. The O2 production rate has been measured showing a performance four times higher than the generally accepted targets for practical applications. The high performance obtained with this device, indicates that there are good perspectives to decrease the O2 production costs significantly decreased as well as small and light weight devices for portable uses are envisaged.