Continuous Spinning Of Piezoelectric PZT Ceramic Fibers And Their Application On 1-3 Type Fiber/Polymer Composites

In this thesis,piezoelectric PZT ceramic fibers were prepared by combination of Sol-Gel processing and Gel-Spinning technique.The structure and properties of PZT fibers were investigated in details.Piezoelectric composites with type 1-3 were fabricated by arranging-casting technique,and their performances were evaluated based on theoretical and experimental results.Eventually,Interdigitated electrodes piezoelectric fiber/polymer composites(IDEPFC) were developed as prototype sensors with obvious sensing properties and anisotropy.Spinnable PZT sols were obtained via precursor-monomer method of Sol-Gel. Several kinds of raw materials were used,including lead acetate trihydrate,zirconium n-butoxide and titanium n-butoxide,in addition to butanol as a solvent and acetylacetonate as a stabilizing agent.The reaction mechanism of precursor hydrolysis and polymerization had been studied.The influences of solvent,water content, stabilizing agent and complexing agent on PZT sols were analyzed.The affects of spinning additive(PVP) on spinning forming and the structure of PZT fibers were discussed.After proper heat treatment,PZT ceramic fibers were obtained.XRD results showed a pure perovskite phase was obtained after heat treatment at 650℃for 1h and a ferroelectric tetragonal phase was achieved after heat treatment at 1000℃for 1h.By using scanning electron microscope(SEM),it was observed that PZT ceramic fibers had dense microstructure with diameter of less than 50μm.EDS results showed PZT ceramic fiber had a stoichiometry close to Pb(Zr_0.52Ti_0.48)O₃.It was confirmed that PZT ceramic fibers had ferroelectric properties with the remnant polarization P_r of 20.9μC/cm² and coercive field E_c of 10.2kV/cm sintered at 1000℃.PZT bulk ceramics were prepared by the same Sol-Gel processing.The structure and properties of PZT bulk ceramics at different sintering temperature were investigated.PZT bulk ceramics had the highest density(7730kg/m³) and the best dielectric properties,piezoelectric properties and ferroelectric properties sintered at 1240℃for 2h.At 1 kHz,the relative permittivity constantεwas 1175 with permittivity loss tanδof 0.004,the piezoelectric strain constant d₃₃ was 285μC/N,the remnant polarization P_r and coercive field E_c were 25.2μC/cm² and 13.5 kV/cm, respectively.The poling condition was optimized.The changes of the relative permittivity constant and permittivity loss after poling were discussed.1-3 type piezoelectric composites were fabricated by arranging PZT fibers and casting epoxy resin.With increasing the ceramic volume fraction,the relative permittivity constant,piezoelectric strain constant and remnant polarization increased of cylindric 1-3 composites.Interdigitated electrodes fabricated by lithography technique were introduced.IDEPFC had a flexible and compliant configuration. Finite element analysis was used to study the magnitude and distribution of the electrostatic field in IDEPFC.A simple in-line electric-field model was employed to analyze and calculate the ferroelectric parameters;the resulted values of the remnant polarization P_r and coercive field E_c were smaller than the cylindric composites with the same ceramic volume fraction.As a prototype sensor,the sensing properties of IDEPFC were investigated.A model analysis verified that the inherent frequency of voltage response produced by direct piezoelectricity of IDEPFC under bending vibration mode was the resonant frequency of IDEPFC.There were periodic output voltages of IDEPFC under harmonic excitation.IDEPFC showed a large piezoelectric anisotropy and had the largest voltage response in the direction along the fibers.The experimental results in this thesis provided some theoretical guidance and practical value for design and fabrication of piezoelectric sensors and actuators.