2019 Volume 66 Issue 4 Pages 158-167
Transparent polycrystalline ceramics, which can be fabricated through sintering processes, have received considerable attentions because those simultaneously possess optical and mechanical properties with relatively high productivity. For attaining the optical transmission in the polycrystalline ceramics, an important factor is to achieve dense and fine grained microstructure. This is because both the residual pores and grain boundaries (GB) become the dominant light scattering sources. Recently, in order to achieve highly transparent ceramics having dense and fine grained microstructures, several external field effects, such as electric, ultra high pressure and magnetic fields, have widely been utilized in the sintering processes. The former two effects can accelerate the powder densification, and hence, enable to attain dense and fine microstructures at relatively low temperatures. The third one can control crystal orientation of polycrystalline ceramics and decrease the light scattering at GB due to the textured microstructure. It is expected that although further improvement of each external field effects is necessary, the advanced sintering techniques that integrate each effect would enhance the development of novel transparent ceramics possessing excellent optical and mechanical properties.
