The dielectric loss (tan ␦) of titanium dioxide (TiO 2 ) disks has been measured at a frequency of 3 GHz. High-purity TiO 2 sintered to almost-full density exhibits a very high tan ␦, which is interpreted to be due to oxygen deficiency. To counter this, doping with stable divalent and trivalent cations, such as Mg and Al, leads to a low tan ␦, probably by preventing Ti 4؉ reduction. The tan ␦ of polycrystalline TiO 2 doped with divalent and trivalent ions with ionic radii in the range of 0.5-0.95 Å at 3 GHz can be very low: 6 ؋ 10 ؊5 (Q Ϸ Ϸ 17 000) at a temperature of 300 K. The tan ␦ of undoped pure TiO 2 disks increases when the disks are cooled from 300 K to ϳ ϳ100 K. At temperatures <100 K, the tan ␦ decreases rapidly, which is interpreted as carrier freeze-out. The tan ␦ for all the high-Q doped TiO 2 polycrystalline samples smoothly decrease to ϳ ϳ5 ؋ 10 ؊6 (Q Ϸ Ϸ 200 000) at 15 K, comparable to that of single crystals.

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Resonators of Ba(Zn1/3Ta2/3)O3, sintered between 1450° and 1600°C, are characterized by Raman spectroscopy, X‐ray diffraction, and scanning electron microscopy. The quality factors of the resonators are found to depend on sintering temperature, and at 1600°C there is evidence of Zn loss from the surface. The frequency of the A1g Raman mode changes from 800.9 cm−1 for a sample with Q= 80000 (2 GHz), to 794.5 cm−1 when Q= 44000 (2 GHz). Changes in the position of this and other Raman modes are thought to be due to distortions of the oxygen octahedra, brought about by Zn loss. The presence of a BaTa2O6 phase at the surface is confirmed by XRD and SEM.

When optical microprobe spectroscopies, based on Raman or luminescence, are used to study materials properties (such as composition or strain) that vary within the volume of material excited by the microprobe, it is necessary to convolute the material property variation with the response function of the microprobe to obtain the observable spectrum. A method for this convolution, in the general case in which the material shows significant absorption of the incident light, is suggested and is shown to give acceptable interpretation of test experiments on alumina and silicon single crystals.