Frabrication And Characterication Of1-3Type PZT/Epoxy Piezoelectric Composites

The purpose of this paper is to frabricate a kind of highly performancedultrasound probe material. With an improved dice and fill method, three kinds of1-3type PZT/Epoxy piezoelectric composites with diffierent PZT volumefraction(58.6%,62%,67.5%) are prepared and each kind of composites are grindedto different thicknesses. Then the DC magnetron sputtering is firstly used to depositNiCr/Ag and NiCr/Cu films as electrodes on the1-3type piezoelectric composites.Finally，the effects of thickness and PZT volumn fraction are studied. The surfacemorphologies of the samples are observed by optical microscope(OM) and scanningelectron microscope(SEM), and the phase composition and structures are analysedby X-Ray Diffraction(XRD). The analytical balance, micrometer, four proberesistivity measuring instrument and precision impedance analyzer are also used totest the experimental results and material properties.The results show that the improved dice and fill method co uld ensure thefracture rate of PZT columns in the piezoelectric composites to be below1%. It isalso found that the choose of raw materials, the diamond blade types, the differentcombination of revolving speed and feeding amount, as well as temperature all havegreat effects on the uniformity of the fabricated1-3type piezoelectric composites.By the analysis and comparison of the electrical property and surfacemorphology of NiCr/Ag and NiCr/Cu films, the conclus ion is that it is moredesirable to sputter NiCr/Ag film less than1μm on the composites as electrodes,because the NiCr/Ag film has lower resistivity and more smooth surface. To makesure that the adhesion strength is strong enough and its thickness does not influencethe radial vibration mode, NiCr film layer is chosen to be about250nm and Ag layerto be about450nm.It is also showed that the volume fraction of PZT in the composites can greatlyinfluence its properties. The electromechanical coupling factor and acousticimpedance of the composite are both better than pure PZT. Under the condition ofsingle mode of vibration, the electromechanical coupling factor could achieve68%while the acoustic impedance is about20Mrayls with the62%PZT. This isattributed to the holding boundary constraint function and elastic boundaryconstraint function of epoxy to PZT columns.At last, the influence of composite thickness on its properties is studied. Theresonant frequency Fsand anti-resonant frequency Fpboth increase with thedecrease of thickness almost by parabolic law. The vibration mode is single whenthe thickness is more than0.145mm, however, the lateral mode becomes evident when it is less than0.125mm. Moreover, the electromechanical coupling factorincreases while the relative clamped dielectric constant decrease with the decreaseof thickness. Moreover, the mechanical loss tangent and the dielectric loss tangentdo not vary obviously.