Research On Low Temperature Co-firing PZT Based Ceramic And Its Application As Multilayer Devices

With the advantages of small volume and high performance, multilayered low temperature cofired piezoelectric ceramic has a wide application in integrated circuit aspect. The key factor of this technology is to choose a piezoelectric ceramic with a good comprehensive performance sintered at low temperature that can be made into film by some method such as tape casting. Pb(Zr0.53,Ti0.47)O3-Sr(K0.25,Nb0.75)O3(PZT-SKN) ceramic has both large d33 values(445p C/N) and high Cure temperature(356℃), becoming a promising material for multilayered low temperature applications. In this study, we substituted sodium for potassium in PZT-SKN based on the lead-free(Na0.5K0.5)Nb O3(KNN) piezoelectric ceramic and developed a new ceramic system: Pb(Zr0.53,Ti0.47)O3-Sr(Na0.25,Nb0.75)O3(PZT-SNN). Through investigations of the influence of SKN/SNN contents, sintering temperature, Cu O content and humidity resistance on the microstructure and properties, we optimized the best composition and sintering process, and made some multilayered low temperature application by tape casting.Firstly, PZT-SKN and PZT-SNN ceramics were synthesized using the conventional solid-state reaction method and their microstructures, dielectric and piezoelectric properties were comparably studied. The result showed that the best properties can be obtained with 1 wt% SKN and 2 wt% SNN at 1175℃, respectively. When 1 wt% Cu O was added, 0.98PZT-0.02 SNN ceramic can be sintered at 900℃ and the properties are: ρ=7.67g/cm3, d33=316 p C/N, kp=0.49, εr=2260, Qm=134.44, tanδ=0.012 and TC=353℃. These ceramics can be used to fabricate multilayer piezoelectric devices with low-melting-point electrodes. Besides, PZT-SNN ceramics showed a higher humidity-resistance characteristic than that of PZT-SKN.Secondly, the film with about 60μm in thickness was obtained by tape casting. Taking the advantages of smooth and defect-free surface, lamination can be made from the as-prepated film.Finally, the process of lamination preparation was explored and well-qualified multilayer piezoelectric device was obtained. Both ceramic and inner electrode showed compact microstructures, and the interface between them is obvious. Besides, there did not appear the seepage phenomenon in the inner electrode. The piezoelectric property improved linearly with the increasing layers. Importantly, the multilayer devices displayed a better sensing performance and were promising candidates for the piezoelectric sensor.