A Viable Route for Dense TiO2 with a Low Microwave Dielectric Loss

Dense, high-purity TiO2 was prepared from commercially available powders. These powders were deagglomerated, colloidally stabilized in aqueous NH3, followed by screening to remove residual agglomerates. Homogeneous compacts were formed using colloidal-filtration followed by sintering. TiO2 with > 99.5% density and 400 MPa flexural strength was obtained at a sintering temperature as low as 1000 degrees C. The dielectric loss of this TiO2 was 1.4 x 10-4 at 6.4 GHz at room temperature. This implied that the product of the quality factor and frequency, (Q x f )=f/tan delta, was 46 000 GHz, similar to 7.6 times higher than 6000 GHz (Q < 2000 at 3 GHz) reported previously. This high-quality factor is attributed to the low sintering temperature as well as a homogeneous dense microstructure with 2.2 mu m grain size. The process described can be applied to realize complex TiO2 structures in new microwave antenna concepts, that require components with a high dielectric constant and low dielectric loss.