Microstructure and electric conductivity of composite (BeO + TiO2) ceramics

Specimens of composite (BeO + TiO₂) ceramics with TiO₂ added in an amount of 5, 10, 20, 30, and 40 mass% are obtained. The temperature dependence of the conductivity of the (BeO + 30 mass % TiO₂) ceramics is studied. Conduction is ensured by the titania additive present in the ceramics in a strongly reduced state. The maximum temperature (950 K) at which the (BeO + 30 mass % TiO₂) ceramics preserves its conductive properties in air for a long time and, possibly, the capacity to efficiently absorb microwave radiation is determined. Heating in air at a temperature exceeding 960 K is accompanied by the processes of oxidation of reduced TiO₂, which causes disordering of the structure and lowering of the conductivity. An electron microscope study is used to show that the distribution of TiO₂ in the BeO of the [BeO + (5, 10, and 30 mass %) TiO₂] system is nonuniform; inclusions of large regions of grouped TiO₂ microcrystals are encountered. This affects the physicochemical properties of the ceramics, the thermal and electrical conductivities in particular. In order to ensure a uniform distribution of TiO₂ in the volume of the ceramics it is recommended to introduce the dioxide into the composition of the BeO powder from solutions (hydrochemical method). __________ Translated from Novye Ogneupory, No. 11, pp. 68–74, November, 2007.