A Study of the Dielectric Properties of Al2O3–TiO2 Composite in the Microwave and RF Regions
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We have studied the effect of addition of titania, as a sintering agent, to alumina on the dielectric characteristics of the ceramic composites obtained. The dielectric properties of the titania–alumina composites were studied by use of impedance spectroscopy and the Hakki–Coleman method in the radio-frequency and microwave regions, respectively. The temperature coefficient of the resonant frequency (τ f ) was also studied. Dielectric permittivity (ε′) was increased and the dielectric loss (tan δ) was improved by addition of titania, as a result of better sintering; addition of 10 wt.% titania resulted in ε′ = 12.68 and tan δ = 8.23 × 10−4 in the microwave region. Increasing the concentration of TiO2 led to inversion of the τ f signal; values were positive when the concentration of TiO2 was >7.5 wt.%. The ceramic composites were evaluated as antennas; for all samples the return loss (S 11) was <−10 dB and the gain was approximately 3 dBi. Addition of 7.5 wt.% titania to the Al2O3 improved antenna performance. In conclusion, addition of the TiO2 to alumina improves its dielectric properties, resulting in the possibility of use of such composites as dielectric resonator antennas (DRA).
KeywordsAlumina titania microwave dielectric properties DRA
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This work was partly sponsored by the CNPq and CAPES (Brazilian Research Agencies) and the US Air Force Office of Scientific Research (AFOSR) (FA9550-11-1-0095).
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