Study On The Ceramic/Polymer Pyroelectric Material And Device

The pyroelectric composites, which are made up of ferroelectric ceramic immersedinto polymer matrix, can combine the excellent properties of both phases, such as highpiezoelectric and pyroelectric activities of the ceramic and the mechanical resistance,formability and flexibility of the polymer. And they have attracted great researchinteresting in the past decades. However, there are still some problems, such as thelower pyroelectric coefficient than single crystal and ceramic, the poor combinationbetween ceramic and polymer, and the poor polarization state of the ceramic phase inthe composite. These drawbacks have great influence on the performance of thecomposite infrared sensor. In order to solve these problems, the optimation of PZTcontent, PZT powders calcining temperature, and Mn doped PZT powder were used toimprove the pyroelectric performance of the composite. Finally, a prototype infraredsensor device based PZT/P（VDF-TrFE） composite was fabricated by laser etchingtechnology.1. The preparation and polarization techniques have been studied in this paper.Hydrothermal synthesized PZT ceramic powders, P（VDF-TrFE）（70:30） powders, andN, N-dimethylacetamide （DMA） solution were mixed to form a suspension. Then thePZT/P（VDF-TrFE） composite films were fabricated by casting using the suspension. Itwas found that the PZT powders were dispersed uniformly and the surface of thecomposite was flat. No serious agglomeration and pores can be observed in thecomposite. It was found that poling the ceramic and polymer step by step was a suitablepoling method for the composite, which will achieve a good polarization state.2. The effects of PZT mass fraction on the microstructure and properties of thecomposite thick film have been studied in this paper. The results showed that, the PZTpowders dispersed uniformly and neither serious agglomeration nor pores can beobserved in the composite when the PZT content was50%. After the PZT contentincreased to60%, the interfaces became rough and the internal porosity increased.When the ceramic mass fraction was50%, the composite got the highest pyroelectriccoefficient, and a little dielectric constant and loss. So the detectivity figure of merit （F_D） of this composite increased greatly than the pure P（VDF-TrFE） composite film,accordingly.3. High temperature calcined PZT ceramic powders were used to improve theproperties of composites in this thesis. It was found that the calcining treatment of PZTpowders can improve the interfaces coalescent of two phases, and show great impact onthe electric properties of composite thick films. When700℃calcined PZT powderswere used as ceramic fillers, the highest pyroelectric coefficient was96μC/m²K, whichincreased20%than that of the uncalcined composites. In addition, the detectivity figureof merit increased about13.5%, accordingly.4. The effects of Mn doping PZT on the properties of composite have been studiedin this paper. Various Mn doped Pb（Zr0.3Ti0.7）1xMnxO3（PZTM_x, x=0,1,2,3mol%）were mixed with P（VDF-TrFE） to fabricate the composite films. It was found that Mndoping can decrease the dielectric constant of PZT, and improve the polarization state ofceramic in the composites. Especially, when PZTM2were used as ceramic fillers, thepyroelectric coefficient and F_Dof the composite reached113μC/m²K and1.77*10^*-5Pa^-1/2, which increased about26%and35%than PZT/P（VDF-TrFE）composite, respectively.5. A2×2mm²composite infrared sensor based on PZT/P（VDF-TrFE） compositethick film with special thermal insulating structure has been developed by lasermicro-etching. Voltage responsivity （RV）, noise voltage （Vnoise）, noise equivalent power（NEP）, and detectivity （D*） were calculated to represent the properties of the compositesensor. When the modulation frequency was5.3Hz, the RVof the infrared sensor wasabout5.2×10³V/W. The highest detectivity （D*） of the infrared sensor was about1.9×10⁸cmHz^1/2W^-1at137.3Hz modulation frequency.