Titanium oxides – electrical all-rounders

At Fraunhofer IKTS, titanium oxides are adapted to customer-specific user requirements, components are manufactured from them and extensively tested. Titanium oxides are characterized by extraordinary variability concerning their oxide compounds. Besides titanium dioxide (TiO₂), which is used for numerous products, such as wall paints, cosmetic products, paper or carriers of catalysts, there are multiple other oxide compositions of tita­nium. Their variable compositions range from Ti₂O to TiO₂. Even a tiny oxygen deficiency in TiO₂ can decrease the electrical re­sistance from 10¹² Ωcm to a level between 10⁵ and 10³ Ωcm. The crystallographic phase change to e.g. Ti₄O₇ shifts the elec­trical resistance to 10^-2–10^-3 Ωcm. Figure 1 illustrates the pro­portions across 15 orders of magnitude of electrical resistivity covered by various titanium oxide types. Furthermore, non-linear correlation of voltage and currency can be created through the doping of TiO₂. Electrical permittivity is particularly high, at a level between 60–800 depending on the applied frequency. Significant oxygen conductivity already sets in at 500 °C. Also of technical interest is the photocatalytic effect, which is par­ticularly linked with the TiO₂ type anatase.

Electro-technical applications

This wide range of properties offers advantages in numerous technical applications: specific materials for electrodes, thermo-electric materials, varistor materials, active catalyst substances, electrical conductors, semi-conductors and insulators or even sensors for oxygen identification and analysis. These applications have a variety of different requirements regarding densification, mechanical strength or oxidation stability. Through the specific modification of the manufacturing parameters, titanium oxide ceramics can be produced as dense and high-strength material or made to be porous and gas-permeable. TiO₂ is completely oxidation-resistant and can be used up to 1500 °C under air. Suboxides are oxidation-resistant up to 400 °C. Furthermore, titanium oxides are chemically stable against almost all reactive substances.

The electrical parameters can be modified to suit almost all ap­plications. Joined compounds of titanium dioxide and titanium suboxides can be produced which combine electrically insulating and electrically conductive parts within a monolithic component (Figure 2).

Services offered

• Adaption of titanium oxides to specific application require­ments
• Manufacture of customer-specific titanium oxide compo­nents
• Implementation of material- and application-orientated investigations and tests