Lithium tantalate - a high permittivity dielectric material for microwave communication systems

Abstract

Lithium tantalate single crystal is characterized by very low thermal expansion and exhibits excellent electro-optical, piezoelectric and pyroelectric properties. We have studied the real part of relative permittivity (/spl epsi//sub r/) perpendicular to the crystal axis and the loss tangent of LiTaO/sub 3/ over the temperature range from 15 K to room temperature at a frequency of 11.4 GHz. The /spl epsi//sub r/ and tan/spl delta/ were determined by measurements of the resonance frequency and the unloaded Q-factor of a TE/sub 011/ mode cylindrical cavity containing the sample under test. The permittivity of LiTaO/sub 3/ was found to change from 38.9 to 41.1 and the loss tangent increased from 1.1 /spl times/ 10/sub -4/ to 6.5 /spl times/ 10/sub -4/ over the temperature range from 15 K to 295 K. Due to the low losses and high permittivity this material can be used in many microwave applications.