Low Temperature Preparation of the Temperature-stable Ba_(0.80)Sr_(0.20)TiO_3/Pb_(0.82)La_(0.12)TiO_3 Composite Thick Films

Sol-gel derived Ba0.80Sr0.20TiO3 and Pb0.82La0.12-TiO3 ferroelectric powders and a low-melting PbO-B2O3 glass powder were mixed to prepare paste. The composite thick films were successfully prepared by screen printing onto the quartz glass substrates with the ITO bottom electrode and then calcined in the sealed silica tube at the low temperature between 550℃ and 750℃. XRD, SEM and LCR were used to measure the structure and dielectric constants of the composite thick films. The results show that the high infiltration of the PbO-B2O3 liquid phase in the thick film gives rise to the ferroelectric powders uniform encapsulated by the PbO-B2O3 phase at the temperature of 750℃ and then the mass transport through the liquid phase, which promote the densification of the thick film. The stable coexistence between the Ba0.80Sr0.20TiO3 and Pb0.82La0.12TiO3 crystal phases can be controlled directly by both the glass phase encapsulated and the diffusion from the particles to the glass phase. The slight reduction of the lattice of the PLT-82 crystal phase in the thick film occurs due to Pb2+ ion vacancy generated by the diffusion. The relative dielectric constant of the composite thick films exhibits the temperature-stable behavior. The variance of the dielectric constants is less than 18% in the temperature range 0-300℃