tailieunhanh - Ferroelectrics Physical Effects Part 2

Tham khảo tài liệu 'ferroelectrics physical effects part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 30 Ferroelectrics - Physical Effects chemical interaction of the film and the substrate the sintering temperature is kept relatively low in comparison to that for the bulk ceramics . 1200 C. This requires additives that form a liquid phase at the sintering temperature. To obtain a PMN-PT thick film with the desired functional response the material has to be dense and without any secondary phase. In the literature the effect of different sintering aids on the densification of thick films was investigated and the best densification and a large increase in the grain size was obtained for the sintering aid Li co Gentile et al. 2005 . The other way that the densification of the PMN-PT can be aided is by the presence of the PbO-rich liquid phase originating from the starting composition containing an excess of Pbo. To keep the liquid phase in the film a lead-oxide-rich atmosphere can be created e. g. using a packing powder rich in Pbo. In the literature the atmosphere was achieved with PbZrOa packing powder with an excess of Pbo short PZ P Gentil et al. 2004 Kuscer et al. 2008 Kosec et al. 2010 Ursic et al. 2088b 2010 or with the packing powder PZ P PMN Gentil et al. 2004 . During heating the Pbo sublimates from the high-surface-area packing powder giving a PbO-saturated atmosphere around the thick film that keeps the Pbo liquid in the film. Since the system is semi-closed the Pbo is lost slowly from the system first from the powder and later from the film. Therefore the time for which the liquid phase is present in the PMN-PT film depends on the amount of packing powder. The process is shown schematically in fig. 2 bottom . The density of the films is proportional to the duration of the liquid-phase sintering and increases with the amount of packing powder up to the limit where the amount of packing powder is too high and after sintering of the film there is still enough Pbo vapour to keep the Pbo in the PMN-PT thick films Kuscer et al. 2008 Kosec et al. 2010 . Pbo .