Crystal chemistry and crystallography of the Ba₂RCu₃O_6+x-SrTiO₃system

Abstract

MgB 2 is a two electronic-bands, two energy gaps superconductor with a high T c of 39K and unusual properties such as temperature and field dependent anisotropy.Superconducting hexagonal single crystals of pure and Al, C, Mn and Fe doped MgB 2 phase have been grown at a pressure of 30 kbar using cubic anvil technique [1-2] to study the intrinsic properties of MgB 2 . The superconducting transition of doped MgB 2 single crystals can be tuned in a wide temperature range between 10 and 39 K by adjustment of the nominal composition. Al [1], Mn and Fe are substituted on the Mg position of MgB 2 and C [2] on the B position. Introduction of disorder by substitution is partly observed.In order to elucidate structure/properties relationships we have carried out x-ray single crystal measurements on doped MgB 2 single crystals (the composition varies between 1 and 15 % doping material). Additional temperature dependent measurements on pure MgB 2 and Mn doped MgB 2 has been carried out.

Chemical reasonableness in Rietveld analysis: Inorganics

“…To explore the influence of cation substitution on crystallographic and other properties, the characterization of solid solution compounds in the (SrO–TiO 2 ): (BaO–TiO 2 ) systems has been undertaken (Wong-Ng et al , 2007). In the (Ba 2− x Sr x )TiO 4 series, it is important to understand the detailed crystallography and crystal chemistry of the intermediate members, since the structures of the two end members are not the same.…”

“…Two of the sites are occupied mainly by Ba and the other two by Sr, but the cation ordering is not complete. A major objective of the study (Wong-Ng et al , 2007) was to determine how the Ba/Sr site occupancies changed as the overall composition varied.…”