Improvement in Perfomances of Low-Temperature Sintered PZT and Application to Smart Ambient Sensors.

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It is concluded from the experimental results on the grain boundaries and the isothermal shrinkage curves of the low-temperature sintered Pb (Zr, Ti) O_3 ceramics with complex oxides, BiFeO_3 and Ba (Cu, W) O_3 additives that the low-temperature sintering process is divided into (1) rearrangement of grains, (2) solution-precipitation or grain boundary diffusion, and (3) grain growth. Therefore, the densification process is enhanced by a formation of liquid phase at the second stage composed of the lead and copper oxides segregated at grain boundary. Furthermore, the sintering temperature has been lowered to 900ﾟC by introducing the pot-milling method.In order to investigate the effects of additives on the electrical properties, the low-temperature sintered Pb (Zr, Ti) O_3 ceramics have been prepared with the various oxide forms of BiFeO_<3-> and Ba (Cu_<0.5>W_<0.5>) O_<3-> related additives. The addition of any combination of the various metal oxides did not change the phase relations. It is indicated again from the density measurement that a Cu component is effective for the promotion of densification at low temperature. The SEM observations reveal that a W component is effective for grain growth at low temnperature. It is also found that the BF-related additives are useful in improving the mechanical quality factor, and the BCW-related additives are useful for improving the dielectric constant.Finally, it is clarified from the measurements on the relative humidity (RH) characteristics of the electrical properties of low-temperature sintered Pb (Zr, Ti) O_3 ceramics that the relative dielectric constant and the dissipation factor increase with an increase in the RH and the electromechanical coupling factor and the mechanical quality factor decrease slightly with an increase in the RH.On the contrary, the dielectric constant is independent on the RH.