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Title: The radio frequency and microwave dielectric properties of doped magnesium oxide
Author: Enayati-Rad, Nasser
ISNI:       0000 0001 3447 9337
Awarding Body: Durham University
Current Institution: Durham University
Date of Award: 1980
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A study of the dielectric properties of pure magnesium oxide and MgO doped with iron or chromium is presented. Measurements were carried out in the frequency range between 5 x 10(^2) Hz and 9.3 x 10(^9) Hz room temperature using a.c. bridge, Q-meter, slotted-line and cavity methods. The basic ideas and principles of each technique have been discussed individually in relation to their suitability for dielectric measurements on materials having particular characteristics. A major attempt has been made to develop the slotted-line technique (500 MHz - 7.5 GH) and the cavity resonator (9,3 GHz) method. Sources of possible error in these techniques have been investigated in detail and some suggestions made to minimize them. A new method for measuring the dielectric properties of low loss solids has been examined theoretically and some suggestions for its practical development pointed out. The dielectric data obtained at room temperature has been analysed and interpreted in terms of the hopping theory involved in the "Universal Law" of dielectric response. The frequency variation of conductivity, followed σ(_ac) (w) (_ɑ) w(^n) law with n = 0.98 ± 0.02 for pure MgO. The dielectric constant, ɛ', loss factor, ɛ'' and loss tangent, Tanδ, decrease slightly over the frequency range. Similar behaviour was also observed for Fe doped MgO and Cr doped MgO samples. The variation of ɛ' and ɛ'' both agree with the "Universal Law" showing that ɛ'(w) (_ɑ) w(^n-1) and ɛ''(w)(^x) w(^n-1); the magnitude of n obtained was also 0.98. The data of ɛ' and ɛ'' approximately fit the Kramers-Kronig relation i.e constant when 0.5
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Solid-state physics