Abstract
Korea Electrotechnology Research Institute, 28-1 Sungju-dong, Changwon, 641-120, Korea(Received July 7, 2000)(Accepted August 9, 2000)Keywords: Shape memory; Ferroelectricity; Multilayer; Interface diffusion; Nucleation and growth1. IntroductionPiezoelectric materials and shape memory alloys (SMA) are widely used for actuator and sensorapplications [1,2]. It is well known that piezoelectric materials produce an electric field when the stressis applied, while it shows deformation when the electric field is applied. The response time ofpiezoelectricity is relatively fast, but the displacement of that is relatively small comparing to the otheractuactors. Shape memory alloys, on the other hand, can produce a large force-displacement duringmartensite-to-austenite transformation. However, the response time of shape memory effect is slowcomparing to that of piezoelectricity, because the shape memory kinetics are controlled by the thermaldiffusivity.Combination of piezoelectric materials with shape memory alloys and formation of the heterostruc-ture are expected to fabricate the advanced materials which show integrated function of piezoelectricityand shape memory property with keeping the function of each material [3,4]. If the heterostructure ofshape memory (TiNi) film and ferroelectric film is heated at the martensite-austenite transformationtemperature, the large force-displacement occurred in the TiNi film layer is supposed to cause thechange of electric field in the ferroelectric film layer. Therefore, the self detection of the displacementcan be performed by monitoring the electromotive force, and the self detection function seems to be theintegration of sensing and actuating function.In order to obtain the smart material, it is necessary to design the heterostructure film without loseingthe functions of each other by means of chemical interaction at the interface. The PZT films wereprepared by sol-gel process, and the TiNi films were deposited on PZT films heated at elevatedtemperatures. On growing the heterostructures, lowering the crystallization temperature of TiNi filmplays an important role in achieving the heterostructure without inter-diffusion. In this study, wedescribe the depositing process of heterostructures. In conjunction with the heterostructures, loweringthe crystallization temperature of TiNi film was also investigated in term of the surface morpology, andthe ferroelectric properties of the PZT layer were measured.2. Exprimental ProcedureTo prepare the piezoelectric film layer, commercially supplied PZT(52/48) precursor solutions wereused. (Kanto Chemical Co.) Partially hydrolyzed 0.5 M precursors were deposited onto Pt/Ti/SiO
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