Temperature dependence of permittivity and loss tangent of lithium tantalate at microwave frequencies

Lithium tantalate (LiTaO/sub 3/) exhibits excellent electro-optical, piezoelectric, and pyroelectric properties and a very low thermal expansion. In this paper, we report measurements of loss tangent and the real part of the relative permittivity (epsilon)/sub r(perpendicular)/ measured in c-axis LiTaO/sub 3/ crystals in the temperature range from 14 K to 295 K at a frequency of 11.4 and 10 GHz. Microwave properties of LiTaO/sub 3/ were determined by measurements of the resonance frequency and the unloaded Q/sub o/ factor of a TE/sub 011/ mode cylindrical cavity containing the sample under test and accounting for uncalibrated cables and adaptors inside the cryocooler. The permittivity of LiTaO/sub 3/ was found to increase from 38.9 to 41.1 and the loss tangent to change from 1.1*10/sup -4/ to 6.5*10/sup -4/ over the full temperature range. Due to its low loss and relatively high permittivity, LiTaO/sub 3/ is suitable for microwave applications.