Attempts were then made to improve

Attempts were then made to improve the density of PZT films via increasing the annealing temperature. When cold sintered PZT tapes were annealed at 900 °C, the PbO remaining from the Pb(NO3)2 melted and served as a sintering aid. [57] Previous work proved the cold sintered PZT pellet reached 99% relative density after 900 °C post-annealing for 3 h. [36] The microstructure of PZT tape annealed at 900 °C on all three types of metal foils is shown in Fig. 4(a)-(c). At 900 °C, cleaner grain boundaries can be observed from PZT compared with 700 °C anneal, but the density of the films was still not satisfactory. The pores are still interconnected, suggesting a relative density < 90%.