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).