Exploratory synthesis is the discovery of new compounds with interesting
structures and properties. The subject of this thesis is exploratory synthesis of
bismuth containing oxides. Bismuth containing oxides have many interesting
properties, which are ionic conductivity, ferromagnetism, superconductivity,
ferroelectricity, ferroelasticity and catalytic. These properties are closely related to
their specific structure which is caused by the lone electron pair effect on Bi ³⁺, in
other words, hybridization of the 6s and 6p states results in interesting
stereochemistry. This can lead to some unusual and potentially useful properties.
Several new compounds BiMn₂NO₆ (N = P, V, As) in the BiMn₂NO₆ family
(M divalent cation, N = pentavalent cation) have been synthesized. The structures
were refined by powder X-ray and neutron diffraction data. The X-ray diffraction
patterns showed these three compounds have similar structures. Like other
compounds in the BiMn₂NO₆ family, they contain (BiO₂)⁻ infinite chains, (AO₄)³⁻
tetrahedral and interspersed M²⁺ cations. Based on these same building blocks, they exhibit their own structure.
BiMnPO₅ compound has been prepared and refined by powder neutron
diffraction data. This material crystallizes in monoclinic symmetry. The structure can
be described in terms of mixed double-chains of two edge-sharing Mn06 octahedral
alternating with two edge-sharing BiO₆ octahedra. The mixed double-chains are
connected to each other through the PO₄ tetrahedra. During the investigation of the
BiMNO₅ family, BiMnVO₅ and BiMnAsO₅ have also been synthesized. Their
structures were determined from X-ray single crystal data. Both of them crystallized
in P1 space group. Bi is five fold coordinated instead of six-fold as for BiMnPO₅,
since the sixth oxygen-bismuth distance is over 3.20Å. This point also shows some
link of the comparable structures between these three new compounds.
Pyrochlore type Bi-Ta(Nb)-Mn-O new compounds were also prepared, the
structures have been determined from X-ray single crystal data. They crystallized in cubic symmetry.
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