Porcelain containing anatase and rutile nanocrystals

The aim of this work is to study the dielectric of two porcelains containing TiO2 in the form of anatase and rutile. TiO2 was added in compositions by means of raw kaolin with a relative high quantity of anatase, or the addition of anatase powder (10 wt%) in the initial mixture. An alternative porcelain containing kaolin–anatase mixture was obtained by a preliminary firing at 1300 °C. Beside kaolin, compositions also contain quartz and alkaline feldspar. The microstructural observations show various crystalline phases and micropores, which also have an effective role in affecting the properties. The dielectric characterization of fired porcelain, in the frequency range of 105–109 Hz, shows that permittivity value can be increased from 7.19 to 8.41, depending in TiO2 crystal type, morphology and content. Permittivity depends also on mullite, quartz and cristobalite, quantities, but the role of TiO2 phase is predominant. The macroscopic permittivity of porcelains can be calculated using a mixing rule, which fit accurately experimental results.