Strontium tantalate ceramics for dielectric resonator and antenna applications
Résumé
Bulk SrTa 2 O 6 ceramics were produced via solid-state reactive sintering, characterized by x-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, and their dielectric properties determined via resonant cavity in the 5G frequency domain. Two polymorphs were obtained. Orthogonal beta phase ceramics, obtaining much lower relative densities, achieved, at -5 GHz, an effective permittivity ( epsilon eff ) of -22, dielectric losses (tan delta ) around 1 x 10 -2 and temperature coefficient of resonant frequency ( tau f ) of around 250 ppm/ degrees . Tetragonal tungsten bronze beta ' phase ceramics achieved relative densities of -87 %, and at -2.8 GHz a higher ' epsilon eff ' between 79 and 85, lower 'tan delta ' around 5 x 10 -3 , and a ' tau f ' of about 300 ppm/ degrees at 90 degrees C. Both phases are found to be Sr -deficient, which may have caused a liquid -phase sintering in the powder bed configuration used for these ceramics. The performance of a prototype dielectric resonator antenna incorporating a beta ' ceramic was demonstrated to validate the measured dielectric properties.