Investigation Of Low Temperature Sintering And Temperature Zone Extension Of PZT Thick Films

Lead zirconate titanate（PZT） materials has been widely used to prepare sensors,transducer and actuator for its excellent ferroelectric, piezoelectric and pyroelectricperformance. Zr-rich PZT is a promising candidate to make infrared detectors because ithas a high pyroelectric coefficient when the transition from rhombohedral ferroelectric lowtemperature phase （FRL） to rhombohedral ferroelectric high temperature phase （FRH） takesplace. Recently, PZT thick films have drawn much attention because they have betterelectrical properties than thin films and it is unnecessary to grind or polish them likepyroelectric ceramics, which is good for miniaturization and integration of device.Compared with other existing methods, screen printing is flexible, cost-effective fabricationmethod for fabrication of thick films.However, the processing temperatures required to obtain dense PZT ceramics areabout1200℃, which is too high for most of substrates and incompatible with the infraredfocal plane array technologies. The LTCC technique also needs to reduce the sinteringtemperature to co-sintered with Ag electrode. With this end in view, reducing the sinteringtemperature is essential for the fabrication and practical application of high performancePZT thick films. The main aim of our research is to reduce the sintering temperature of PZTthick film to below the melting point of silver and improve the electrical of PZT thick films.First of all, the Pb(Zr_0.9Ti_0.1O₃thick films were fabricated on Al2O3substrate via thescreen printing technology by using Bi₂O₃-Li₂CO₃additions as liquid-phase sintering aids.The dependence of microstructure, dielectric and pyroelectric properties on the content ofsintering aids has been studied. When a proper quantity of Bi₂O₃-Li₂CO₃doped in the thickfilms, the sintering temperature of the thick films decreases to1050℃, and the grain size,density and electrical of the thick films increase. The Pb(Zr_0.9Ti_0.1O₃thick film with6wt%Bi₂O₃-Li₂CO₃has the maximum pyroelectric coefficient4.5×10^-8Ccm^-2K^-1and the highestfigure-of-merit2.3×10^-5Pa^-1/2at30℃.Then, in order to reduce the sintering temperature of the PZT thick films to900℃,PbO and Bi₂O₃-Li₂CO₃were chose as liquid-phase sintering aids. The effects of sintering aids doped on the microstructures, phase compositions, dielectric properties andpyroelectric properties of the thick films were systematically investigated. It was found thatwhen the amount of Bi₂O₃-Li₂CO₃increases, the sintering temperature of the thick filmsdecreases from1100℃to900℃, and the grain size and the lattice constant decrease either.In addition, the Pb(Zr_0.9Ti_0.1O₃thick film with6.4wt%PbO and5.4wt%Bi₂O₃-Li₂CO₃sintered at900℃has the maximum pyroelectric coefficient10.51×10^-8Ccm^-2K^-1and thehighest figure-of-merit10.58×10^-5Pa^-1/2.In order to solve the problem that the pyroelectric temperature zone was too narrowwhen PZT thick film was used in infrared sensor, the multilayer thick film with widepyroelectric temperature zone was prepared. To prevent the reacting between componentsin the different layer, the starting materials were pretreated. The multilayer PZT thick filmhas the pyroelectric coefficient larger than5.5×10^-8Ccm^-2K^-1, the figure-of-meritapproximately6×10^-5Pa^-1/2, in the pyroelectric temperature zone（17℃³5℃）.