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

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 (ε_r) 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 ε_r 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.