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 (εr) perpendicular to the crystal axis and the loss tangent of LiTaO3 over the temperature range from 15 K to room temperature at a frequency of 11.4 GHz. The εr and tanδ were determined by measurements of the resonance frequency and the unloaded Q-factor of a TE011 mode cylindrical cavity containing the sample under test. The permittivity of LiTaO3 was found to change from 38.9 to 41.1 and the loss tangent increased from 1.1 × 10-4 to 6.5 × 10-4 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.