Study Of Lead-based Pyroelectric Thick Films Using Gel-tape-casting Process

Zr-rich PZT ceramics are potentially promising materials in infrared detecting, thermal imaging and heat-electric energy converting, because of their high pyroelectric coefficient and low dielectric constant during the FRL-FRH phase transition. However, the temperature range of FRL-FRH phase transition of this ceramics material is narrow, which is only 2-4℃, and FRL-FRH phase transition is first order transition which can result in thermal hysteresis, so the application of this ceramics in heat-electric energy converting and IR detecting is limited. In order to overcome the limitation of the single composition ceramics material, this work investigated to fabricate overlaped thick film ceramics to expand the temperature range of FRL-FRH phase transition.At first, single composition PZT95/5 and PZT85/15 doped with Nb, Sb, Mn monolayer pyroelectric thick films were prepared by gel-tape-casting. The optimal pyroelectric composition of gel-tape-casting slurries was determined through gel-tape-casting experiment, The inhibition of oxygen, which occurred in gelcasting during the formation of polymer networks, was successfully prevented by isolating air effectively。Smooth and relative high density thin pyroelectric ceramic films were got by "sandwich" sintering. The pyroelectric properties of samples made by tape casting are favorable。The PZT95/5 thick films'begin temperature of FRL-FRH phase transition is lower than PZT85/15,which is close to room temperature。And the peak value of pyroelectric coefficient is higher. But the pyroelectric coefficient of PZT85/15 is smooth after FRL-FRH phase transition, the pyroelectric coefficient of PZT95/5 descends after FRL-FRH phase transition. The pyroelectric coefficient p of PZT95/5 is 5×10-8C/cm2K at 20℃, The pyroelectric coefficient pmax is 8.5×10-8C/cm2K at 30℃when FRL-FRH phase transition happens. The pyroelectric coefficient p of PZT85/15 is 2×10-8C/cm2K at 20℃, The pyroelectric coefficient pmax is 7.5×10-8C/cm2K at 50℃when FRL-FRH phase transition happens.Based on the preparation of monolayer films, overlapped thick films were preparated. The interior overlapped thick films were uniform, without delamination and microcracks existed. The pyroelectric coefficient p of overlapped thick films is 5×10-8C/cm2K at 30℃, The pyroelectric coefficient pmax is 7.5×10-8C/cm2K at 40℃when FRL-FRH phase transition happens. The pyroelectric coefficient doesn't descend after 40℃. Due to the expanding of temperature of phase transition, it can applied in infrared detecting and heat-electric energy converting.This paper touches upon preparing thick films on Si substrates with gel-tape-casting and novel Sol-Gel method。Due to the addition of sintering aid, the sintering temperature descended to the tolerance of Si substrates. The nanometer particles and polyviny pyrrolidine ( PVP) are dispersed uniformly into the sol-gel precursor solution to prepare pyroelectric thick films on Si substrates.