Publications

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Pb-based ferroelectrics are useful because of their large dielectric constants, high polarization values, and strong piezoelectric coefficients, but typically require sintering temperatures >1200 C, which leads to loss of the volatile Pb cation and necessitates the use of Pt electrodes for cofired parts. Reduced sintering temperatures can minimize lead loss and enable the use of cheaper electrodes, but must not sacrifice electrical performance. A systematic study of dopants to lower the sintering temperature of PNSZT (Pb0.992 (Zr0.815 Ti0.05 Sn0.135)0.9845 Nb0.155 O3) led to densities greater than 98.5% of theoretical at temperatures as low as 1100 C with as little as 0.2 wt% of a Pb glass additive or as high as 98% at 900 C with Cu2O additions with equivalent electrical properties to undoped materials.

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The Materials Chemistry Department 1846 has developed a lab-scale chem-prep process for the synthesis of PNZT 95/5, referred to as the ''SP'' process (Sandia Process). This process (TSP) has been successfully transferred to and scaled-up by Department 14192 (Ceramics and Glass Department), producing the larger quantities of PZT powder required to meet the future supply needs of Sandia for neutron generator production. The particle size distributions of TSP powders routinely have been found to contain a large particle size fraction that was absent in development (SP) powders. This SAND report documents experimental studies focused on characterizing these particles and assessing their potential impact on material performance. To characterize these larger particles, fractionation of several TSP powders was performed. The ''large particle size fractions'' obtained were characterized by particle size analysis, SEM, and ICP analysis and incorporated into compacts and sintered. Large particles were found to be very similar in structure and composition as the bulk of the powder. Studies showed that the large-size fractions of the powders behave similarly to the non-fractionated powder with respect to the types of microstructural features once sintered. Powders were also compared that were prepared using different post-synthesis processing (i.e. differences in precipitate drying). Results showed that these powders contained different amounts and sizes of porous inclusions when sintered. How this affects the functional performance of the PZT 95/5 material is the subject of future investigations.