The phosphor cation retards BaTiO3 formation during the first reaction stage, and favours Ba2TiO4 formation. As a consequence, the end of the reaction is only accomplished at 1150 degrees C. The average particle size of the synthesized powder, after attrition milling was < 1.0 mu m. Isopressed bars were sintered from 1200-1400 degrees C. Dilatometric measurements showed the existence of two sintering mechanisms; these were confirmed by means of isothermal sintering experiments. Microstructural development at low sintering temperature differs from that corresponding to higher ones. Very high permittivity values were measured in the 1325-1350 degrees C sintered samples. This anomalous dielectric behaviour is associated with the presence of phosphor.