Browsing by Author "Abd Ellah, RA"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Study of thermal currents in powder beta-spodumene ceramics doped with CuO, FeO and TiO2
    (BELGIAN CERAMIC SOCIETY, 2002) Ragab, HS; Abd Ellah, RA; Ellil, MSA; Osman, WH
    Ternary - phase ceramic system of Li2O Al2O3 4 SiO2 doped with CuO, FeO and TiO2 has been prepared and subjected to d.c. electrical conductivity and thermally stimulated depolarization current (TSDC) measurements as a function of temperature (30-250 degreesC) and field strength. The electrical conductivity results are explained by assuming both ionic and electronic conduction mechanisms coexist with different contributions over the whole temperature range of experiments. TSDC spectra have been found to be characterized by a broad intense relaxation peak which can be attributed to an ionic charge polarization, The broad relaxation transitions are apparently a result of the nonuniform nature of this process. Activation energies are calculated for both d.c. electrical conductivity and TSDC according to Arrhenius equation and initial rise method respectively.
  • Thumbnail Image
    Item
    Thermally stimulated depolarization currents in gamma-irradiated beta-spodumene solid solution ceramic
    (KLUWER ACADEMIC PUBL, 2001) Ragab, HS; Abd Ellah, RA; Abo Ellil, MS; Shehab, A.; Basha, AF; Abd El-Kader, FH
    Thermally stimulated depolarization currents (TSDC) in unirradiated and gamma -irradiated press prepared beta -spodumene solid solution ceramic have been investigated within the wide temperature range 20-160 degreesC. Doses in the range 10-10(5) Gy were used. The TSDC spectrum at relatively high polarizing fields shows two relaxation peaks whose positions and intensities depend on the polarization conditions and gamma -doses. Discussion of data is given on the basis that dipolar and space-charge polarization coexist in the used ceramic material. Activation energies for space-charge peak are determined from the initial rise of thermal current peak under different gamma -doses. Aging effect clearify that the longer the aging time, the smaller the polarization. Pyroelectric current data provide further support to space charge effects. (C) 2001 Kluwer Academic Publishers.