Influence of La2O3, SrO, and ZnO addition on PZT

Effect of ZnO, SrO, and La2O3 additions on properties of lead zirconate titanate (PZT) nanopowder were investigated. Our objective was to densify PZT near 900 degrees C to reduce lead loss and increase processing compatibility of these materials with IC fabrication technique for micro-electro-mechanical systems (MEMS). PZT nanopowders were synthesized using citrate nitrate autocombustion method. ZnO was used as sintering aid, which promoted liquid phase sintering. With only 2 wt% ZnO addition, 93% theoretical density was achieved after sintering at 900 degrees C for 1 h. SrO and La2O3 were used as A-site dopants in PZT to improve dielectric properties. Different amounts of SrO, La2O3, and a combination of both were added in 2 wt% ZnO-doped PZT. Between 93% and 95% of theoretical densities were obtained in all cases after sintering at 900 degrees C for 1 h. X-ray diffraction analysis revealed that increase in SrO content increased tetragonal phase formation. However, addition of La2O3 stabilized both tetragonal and rhombohedral phases. Increase in SrO content increased the dielectric constant of PZT with a maximum dielectric constant of 1800 for 1 wt% SrO and 2 wt% ZnO sample. It was observed that an increase in La2O3 up to 2 wt% increased dielectric constant, and the highest dielectric constant obtained was 1500. Combination of both SrO and La2O3 addition showed even higher dielectric constant than their individual contribution. Highest dielectric constant of 2100 was measured for 2 wt% La2O3, 1 wt% SrO and 2 wt% ZnO-doped PZT which was sintered at 900 degrees C for 1 h. This is one of the highest dielectric constant reported for PZT ceramics that was sintered below 1000 degrees C.