Identification of surface phases on BaTiO3 TiO2-Ceramics.

The triangular and hexagonal crystals which form during annealing on the surfaces of ceramics in the BaTiO3-TiO2 system have been identified as Ba3(PO4)2. The primary source of phosphorus is the TiO2 raw material which contains =0.2 wt % as P2O5. During sintering at >=1300C the phosphorus is well distributed presumably as a glass film at the grain boundaries. After annealing at =1275C the phosphorus concentrates at the surface as Ba3(PO4)3 crystals. The form of the phosphorus in Ba2Ti9O20 and indeed its very presence may have important effects on microwave loss quality Q.