Zinc Oxide Doped Red Sea Egyptian Clay as a Varistor

M. El-Hofy; M. Dawoud; M. Elkhatib; A. Abdel Aziz

doi:10.4028/www.scientific.net/KEM.605.7

Paper Titles

Preface and Scientific Committee

Electrochemical Sensor for Monitoring RedOx Potential of Molten Salts
p.1

Zinc Oxide Doped Red Sea Egyptian Clay as a Varistor
p.7

The Fabrication and Characterization of Niobium-Doped Titania Ceramic
p.11

Chemical Sensor Array Modeling: Application to Resistive Based Chemo Sensors
p.15

Fluorescent Probes for the Selective Detection of Cysteine in Water
p.19

IR Thermography and Resistivity Investigations on Ni-Ti Shape Memory Alloy
p.23

Dislocation Density Effect on Thermal Diffusivity of AISI 316 Steel
p.27

HT-XRD Analysis of W Thick Coatings for Nuclear Fusion Technology
p.31

HomeKey Engineering MaterialsKey Engineering Materials Vol. 605Zinc Oxide Doped Red Sea Egyptian Clay as a...

Zinc Oxide Doped Red Sea Egyptian Clay as a Varistor

Abstract:

Clay consists of about 50% SiO₂ + 25% Al₂O₃ plus some other oxides with low abundance ratio like CaO, TiO₂, Fe₂O₃, MgO and Mn₂O₃. Burning the clay at 700°C removes out the organic compounds and the mentioned oxides only remain. Our aim is to dope ZnO by the remaining oxides for varistors fabrication. Six types of clay were collected from Egyptian Red Sea Coast mines, after burning for 2 hrs the remaining oxides were mixed and ball milled with ZnO for 10 hrs according to the formula (100-Xn) ZnO +Xn, where n is the clay type and X is the ratio of the clay in grams, X takes the values 0.525 in 15 steps. Samples were pressed and sintered at three different temperatures (T_sin) 1200°C, 1300°C and 1400°C for 1 hr, and then studied via XRD, SEM, EDAX, J-E and C-V measurements. The obtained results were discussed in terms of the microstructure of the samples and the formation of Schottky barriers. Barrier height Ф, width W, interface state density N_s and donor state density N_d were calculated for the samples with highest nonlinearity α. It was found that the breakdown electric field E_o is related exponentially with the ratio of Zinc silicate phase whereas α scales with ratio of ZnO phase and the later increases linearly with T_sin. The electrical characteristics of the most promising sample were compared with those of ZnO samples doped pure SiO₂ and Al₂O₃ obtained at the same preparation condition. This sample is comparable with the Japanese commercial varistor 5N220k Dc JVR.