The Manufacture And The Electric Properties Of Porous PZT Ceramics

The interest in 3-3 piezocomposite materials is due to they are of high sensitivity and in better impedance matching of the composite with water and biological tissues. According to the reported literatures and analysing the researches and the development of the 3-3 piezoelectric composites, choose porous PZT as disquisitive object, take the air in the pores as the second phase, research their preparation and properties, provide academic and experimental data for 3-3 piezoelectric composites.Piezoelectric porous lead Zirconate titanate (PZT) ceramics were prepared by two step annealing method using PbO₂ ZrO₂ and TiO₂, the results showed that the bulks sintering on burning out the additives can ease up the stress in the bulk,decrease the content of the cubic phase in some way. The XRD and Raman anylysis were used to analyse the constructive of the phase and atructure. According to SEM and the porosity, steady porosity can be obtained while pressed on 120MPa,the porosity increases with the addition of the pore former agent,the size and shape of the pore are decided by the additive;the smaller the size of the raw material,the lower porosity will obtained;the porosity decreased with the increase of the sintering temperature.The influence of the sintering temperature to the piezoelectric and dielectric properties have been investigated. The grain size increases with sintering temperature ,which decreases the "fix" effect of the grain boundaries and domain walls and leads to an increase of the dielectric constant and a decrease of the piezoelectric constant, the result proves1250℃is the best sintering temperature.The relationship of the pore shape and porosity with the dielectric and piezoelectric properties of the porous PZT has been studied by an analytical model of '3-3 type which accord with the experimental results well: in a fixed porosity, as pores are elongated in the direction of poling, the volume fraction of material contributing to dielectric constant (ε₃₃) and piezoelectric constant (d₃₃) increases, which improves both theε₃₃ and d₃₃, and leads to an increase in hydrophone charge (d_h) and voltage (g_h) a while used as a hydrophone,so does the hydrophone figure of merit (FOM), but the acoustic impedance has no changes. When the porosity is less than 50%,theε₃₃ and d₃₃ decrease with the increase of porosity when the d_h ,g_h and FOM are all increased, the acoustic impedance is also improved.Compared the analytiacl model with Banno modified cubic model,the former pay attention to the influence of the pore shape to the physical properties and predict the change of properties cerrect while the latter told the properties vary with the porosity while the porosity changes in a low porosity range.