Sintering of Si3N4 with Li-exchanged zeolite additive

This paper deals with the densification and phase transformation of Si3N4 with additives of Li-exchanged zeolite during pressureless sintering at significantly reduced temperatures. Dilatometric shrinkage data show that the first liquid forms as low as 1080 degrees C. Upon sintering at 1500 degrees C the bulk density increases to more than 95% of the theoretical density without phase transformation from alpha-S3N4 to beta-Si3N4, i.e. the phase transformation lags behind the densification process. Above 1500 degrees C the secondary phase is completely converted into a glass and the alpha-to-beta transformation takes place. Under these conditions the grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. The results show that a very effective low-temperature sintering additive for silicon nitride can be obtained from Li-exchanged zeolite

Effect of LiYO(2) addition on sintering behavior and indentation properties of silicon nitride ceramics

The influence of the sintering additive LiYO(2) (5-15 wt.%) on sintering behavior, microstructure and mechanical properties of Si(3)N(4) ceramics was investigated. Since LiYO(2) enables densification of Si(3)N(4) at extraordinarily low temperatures, sintering was carried out in the range from 1200-1700 degrees C. Densification was found to be enhanced with increasing additive content due to an increasing volume fraction of the liquid. The phase transformation and grain growth occurred through a solution-reprecipitation mechanism, where the precipitation took place preferentially on pre-existing beta-Si(3)N(4) nuclei (of which the starting powder already contained 20 wt.%). The indentation fracture toughness increased with both sintering time and additive content as a result of the growth of elongated grains

Electric Fatigue in Ferroelectric Lead Zirconate Stannate Titanate Ceramics Prepared by Spark Plasma Sintering

Ferroelectric lead zirconate stannate titanate ceramics were prepared by spark plasma sintering (SPS). Compared with its counterpart densified by conventional sintering (CS), the SPS material shows a smaller remanent polarization and maximum strain as well as a higher coercive field. Electric fatigue in both materials was investigated. In contrast to CS samples, the SPS specimens show a lower resistance to bipolar electric cycling, characterized by a faster decrease in remanent polarization and maximum strain at cycle number below 10^6.5 and a subsequent slower reduction of the properties at high cycle numbers up to 10^8

Electric Fatigue in Ferroelectric Lead Zirconate Stannate Titanate Ceramics Prepared by Spark Plasma Sintering

Ferroelectric lead zirconate stannate titanate ceramics were prepared by spark plasma sintering (SPS). Compared with its counterpart densified by conventional sintering (CS), the SPS material shows a smaller remanent polarization and maximum strain as well as a higher coercive field. Electric fatigue in both materials was investigated. In contrast to CS samples, the SPS specimens show a lower resistance to bipolar electric cycling, characterized by a faster decrease in remanent polarization and maximum strain at cycle number below 10^6.5 and a subsequent slower reduction of the properties at high cycle numbers up to 10^8