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The influence of the method used for preparing As 2 Se 3 amorphous layers on the processes of charge transfer and charge accumulation in these structures is studied. Different physical parameters, such as the contact capacitance, the width of the charge accumulation region, and the time of transit of charge carriers through the samples, which characterize the occurring electronic processes, are determined for the layers under investigation.

AbstraeC The aim of the paper is to study the electrical and thermal properties of Bi203, PhO and mixed oxides of Bi,O,-PhO system (Bi,2Ph0,, and BiaPb20,,). The specific dark conductivity of structures under study was found to be quite low -IO -I 2 10." R -l.m-'at room tern perature. Thermal conductivity of Bi203, PhO and bismuth-lead-oxide compounds were found to he quite high: 1.3 -2.2 WimK. The paper also reports on the investigation of temperature dependence of thermal conductivity within the temperature range 290-670 K. INTRODUCITONLead and bismuth oxides have been the subjects of extensive study in last decades: due to their peculiar properties they have raised much interest for industrial application. Bismuth-lead-oxide compounds are less studied. J.C. Boivin and et.al. [1-2], R.M. Biefeld and S.S. White [3] and later N.M. Sammes and et.al. [4], N. Anisimova and G. Bordovsky [SI investigated Bi203-Pb0 system. The addition of PbO to Bi203 induces a range of phases stable or metastable at room temperatures depending on the dopant concentration. Much controversy exists as to how many compounds there are in Bi,O,-PbO system.However it has been generally accepted the existence of three compounds:1 -the sillenite structure BillPhOIP (6Bi20,-Pb0, 14.3 mol.% PbO) was found to have bcc structure; 2 -BkPb20,, (3Bi,03-2Ph0) formed at dopant level 40 mol.% PbO with hexagonal structure appeared to be stable over a very narrow composition range; 3 -B&Ph,Oll (4Bi20,-5Pb0) formed at 55mol.% PhO was found to have a tetragonal structure. EXPERIMENTAL RESaTS AND DISCUSSIONLead and bismuth oxides and bismuth-lead-oxide corn pounds are highly resisted semiconductors with specific dark resistivity of the order of 10" ~ IO" 0 . m at room temperature. The temperature coefficients of resistivity (TCR) for all oxides are found to he not high in the tern perature range 290 -400 K. The conductivity is of impurity character (in the same temperature range) and is due to charge carrier release from local states in the forhidden band gap. The activation energy of these states is listed in the table. Current-voltage characteristics of oxides are typical for space charge limited currents. Space charge dispersion in the oxides is followed by electrical 0-7803-8348-6/04/$20.00 02004 IEEE. ivity, W /~K I break down. Information about characteristics of Bi20,, PhO, B&PhlOll and Bi12PhOlois listed in table 1. Heat transfer in Bi,O,, PhO and bismuth-lead-oxide corn pounds was studied. Thermal conductivity and its tern perature dependence within the temperature range 290-670 were obtained. Heat conduction ability of oxides under study was estimated in terms of Keyes equation: 1where TMis a melting temperature, dis a density of an oxide, A ~ is its atomic mass, Bis a constant (its value depends on the nature of bonds in a crystal). The estimated thermal conductivity of the oxides was found to he quite high: 3.5 -2.46 WlmK. Table 1.

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