M. A. Mousa, A. A. El-Khouly, E. A. Gomaa and A. A. M. Aly

Electrical Conduction in γ-Irradiated- and Unirradiated-Pure and Doped Samples of Cr2O3

De Gruyter Oldenbourg | 2017
DOI: https://doi.org/10.1515/zpch-1986-26716
Z. phys. Chemie, Leipzig 267 (1986) 1, S. 125-130 Department of Chemistry, Faculty of Science, Mansoura University, Mansoura {Egypt.) Electrical Conduction in y-Irradiated- and Unirradiated-Pure and Doped Samples of Cr203 By M. A. Mousa, A. A. El-Khooly, E. A. Gomaa1 and A. A. M. Aly1 With 1 Figure and 2 Tables (Received 20th March 1984) Summary The electrical conductivities (a) of pure and doped Cr203 samples were measured at a temperature range of 25-450°C and the activation energies were also calculated. The doping elements used were Li, Be, Mg, Zn, Ni, Sb and Ti in a concentration range of 0.01-2.0 atom- %. The first five cations have been seen to increase the electrical conductivity and decrease the activation energy (£,) of the pure Cr203, whereas, the last two cations (Sb and Ti) showed a reverse behaviour. All these observations have been interpretated and discussed in this publication. Moreover, the same determinations of electrical conductivity and activation energy were also achieved for the y-irradiated samples of pure Cr203 using two different doses of y-rays at the same range of temperature, 25-450°C. The values of the rate constant (k) of the recombination process of the defects produced by y-ir-radiation were determined at a temperature range of 500-1400°C and the E„ calculated was found to be 0.03 eV. Introduction It is well known that Cr203 can be considered as an oxygen semiconductors [1, 2] with a band gap [3] of 3.4 eV. The addition of divalent ions M2+ (such as Mg2+ and Ni2+) as impurities was observed to increase the number of the acceptor state, whereas the addition of tetravalent ions, M4+ (e.g. Ti4+) was observed to reduce that number [4]. It was decided to study in detail the effect of the addition of some doping elements, with different valences than that of Cr3+, on the electrical conduction process. More-over, the effect of y-irradiation on the electrical conductivity of undoped Cr203 was one of our target as well. Experimental Pure samples of fine powder Cr203 were obtained by the thermal decomposition of a BDH, (NH4)2Cr207. Various calculated amounts of impurities such as Li, Be, Mg, Zn, Ni, Sb and Ti were mixed With pure Cr203 prepared as mentioned above to give the doped samples. Each of these doped samples was compressed into a disc (7 mm diameter and 10 mm thick), then it was heated up to 1400°C for about 48 hours. Each disc was cut into a rectangular one and it was used for dc-conductivity measure-ments. The resistance of each of these discs was measured using the 4-probe method, whereas the disc ends were silver coated and two Ag-leads were positioned around the 1 Dr. M. A. MOUSA, Chemistry Department, Faculty of Science, Benha University, Benha, Egypt, and A. A. EL-KHOULY and E. A. GOMAA, Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt. 2 A. A. M. ALY, Chemistry Department, Faculty of Science, Assiut University, Assiut, Egypt.
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Zeitschrift für Physikalische Chemie
Zeitschrift für Physikalische Chemie
Volume 267O Issue 1
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