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| Naji, M. |
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Hartnett, John G.
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Topics
Publications (7/7 displayed)
- 2011Microwave properties of semi-insulating silicon carbide between 10 and 40 GHz and at cryogenic temperaturescitations
- 2010Detrapping and retrapping of free carriers in nominally pure single crystal GaP, GaAs, and 4H–SiC semiconductors under light illumination at cryogenic temperaturescitations
- 2009Measurements of the complex permittivity and the complex permeability of low and medium loss isotropic and uniaxially anisotropic metamaterials at microwave frequenciescitations
- 2008Modified permittivity observed in bulk gallium arsenide and gallium phosphide samples at 50 K using the whispering gallery mode methodcitations
- 2004The microwave Characterization of Single Crystal Lithium and Calcium Fluoride at Cryogenic Temperaturescitations
- 2004The dependence of the permittivity of sapphire on thermal deformation at cryogenic temperaturescitations
- 2003Lithium tantalate - a high permittivity dielectric material for microwave communication systemscitations
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article
The dependence of the permittivity of sapphire on thermal deformation at cryogenic temperatures
Abstract
The whispering gallery mode technique applied to single crystal sapphire, doped with trivalent and tetravalent ions of titanium, has been used as a precise method of determining the dependence of the permittivity of pure sapphire on temperature-induced dimensional changes. According to the one-phonon model this is a measure of the temperature dependence of the polarizability of the dielectric. The fractional change in the square root of the permittivity near 17 GHz was found to be related to the fractional change in dimensions resulting from thermal expansion by a factor of 16.0 ± 0.7, between 20 and 90 K. This was found to be the same both parallel and perpendicular to the crystal axis in monocrystalline sapphire. Only the anisotropy in the thermal expansion coefficient causes a difference between the temperature coefficients of permittivity parallel and perpendicular to the crystal axis.