ABSTRACT The anisotropic loss tangent has been determined in monocrystalline sapphire for components parallel and perpendicular to the crystal axis, using the whispering gallery (WG) mode method. The Q-factors of quasi-TE and quasi-TM modes were measured precisely in four cylindrical sapphire resonators at room temperature, from which was determined a maximum attainable Q-factor of (2.1± 0.2)× 105 at 9 GHz in a quasi-TM mode. Sapphire dielectric material from three different manufacturers was compared over the 270--345 K temperature range and the 5--16 GHz frequency range.
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