City Research Online

Abstract

The electronic processes responsible for the observed semiconducting properties in various main group chlorides, bromides and iodides is, studied. Particular attention is paid to compounds containing iodide and a main group element in its lower oxidation state and therefore containing a non - bonding electron pair.

The design and construction of apparatus to measure the effect of temperature on electrical conductivity and photoconductivity is presented.

Materials of the type (mathematical equation, refer to thesis abstract) are prepared and characterised. The optical properties, bulk and surface electrical conductivities and photo conductivities of the phases are measured and the results related to compositions of phases and their electronic structure. The room temperature absorption and reflectance data for all phases studied gave absorption edges and are attributed to band-to-band rather than atomic transitions. The optical and electrical Properties of the iodide systems studied are indicative of a cationic mechanism with the exception of the (mathematical equation, refer to thesis abstract) system where impurities are definitely involved all other systems can be explained in terms of donation of main-group ns electrons to a conduction band formed by overlap of empty halide orbitals. A mechanism involving population of empty solid state bands by iodine electrons themselves cannot account for any of the experimental data for compounds containing ns elements. The mechanism of halide band formation and reduction of the distorting effects of the lone-pair electrons is described in terms of orbital energy matching.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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