Preparation And Characterization Of Oriented Through-hole Piezoelectric Ceramics

Piezoelectric ceramics are widely used in different aspects.But when dense piezoelectric ceramics are used in underwater acoustic transducers,the loss of energy is too much.The introduction of pores can solve the problem of energy loss.How to maintain the high electrical properties of porous piezoelectric ceramics has become a hot spot of the current research.In this thesis,porous PZT green bodies with a solids content of 20?40 vol%were fabricated by casting.Tert-butanol(TBA)was applied as the pore-forming agent and polyvinyl butyral(PVB)was applied as the binder.The green bodies were subsequently freeze-dried and sintered to yield porous piezoelectric ceramics.The paper studied the influence of solids content and sintering temperature on the structure and properties of porous PZT ceramics.It was found that the pores in the prepared porous PZT ceramics are arranged one-dimensionally along the direction of the temperature gradient of freeze-drying.With the help of X-ray diffraction analysis on the longitudinal section of the porous ceramic,it was found that the intensity of its(002)characteristic peak was very low.It shows that the prepared PZT porous ceramics have(002)preferred orientation along the length of the pores.When the solid content was 40 vol%and the sintering temperature was 1250?,the porosity of PZT ceramics was 40%,and the piezoelectric coefficient d₃₃ of the sample reached 680 p C/N,which is almost equivalent to the piezoelectric performance of compact piezoelectric ceramics.The dielectric constant of the porous ceramic sample was 900,and the dielectric loss was7%.Then we explored the preparation of oriented BNT porous ceramics by freezing-casting method based on the research of PZT porous piezoelectric ceramics.The effects of solids content and sintering temperature on the structure and properties of BNT ceramics were studied.The study found that the solid content in the range of 20-30 vol%can obtain porous piezoelectric ceramics with directional through-hole structure.The prepared BNT ceramic has good electrical properties at 30 vol%solid content and1170°C sintering temperature.The piezoelectric coefficient of BNT porous ceramics reached 60 p C/N.The relative dielectric constant is 553 and the dielectric loss is 1.5%.It has high porosity of 40vol%.