Modification of Deposition Process of Piezoelectric Polycrystalline Film by Hydrothermal Method -Improvement of the Depo
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Modification of deposition process of piezoelectric polycrystalline film by hydrothermal method -Improvement of the deposition process by pre-treatment using hydrogen peroxide Akito Endo1, Norimichi Kawashima1, Shinichi Takeuchi1 Mutsuo Ishikawa2 and Minoru Kurosawa2 1 Toin University of Yokohama, Department of Biomedical Engineering, 1614 Kurogane-cho, Aoba-ku, Yokohama, Kanagawa, 225-8502, JAPAN 2 Tokyo Institute of Tecnology, 4259 Nagatuta-machi, Midori-ku, Yokohama 226-8503, Japan
ABSTRACT
We have studied on hydro-thermally synthesis of Pb(Ti,Zr)O3 (PZT)piezoelectric polycrystalline thick film on titanium (Ti) substrate. The purpose of this study is resolving the problems for application of PZT hydrothermal polycrystalline thick film to the ultra miniature high frequency medical ultrasound array probe. The problems were the existence of pinholes in the deposited PZT film, the rough surface of that, low dielectric breakdown electric field etc. The surface of Ti substrate was pretreated to have hydrophilic property by using high reactivity of hydrogen peroxide for resolving the problems in this study. As results, hydrophilic property on the surface of Ti substrate was improved. Surface of PZT hydrothermal polycrystalline thick film without pinholes and smooth surface of that were obtained. Furthermore, the material properties like density, Young’s modulus and piezoelectric constant d31 were increased by the pretreatment of Ti substrate. Consequently, dielectric breakdown electric field of PZT hydrothermal polycrystalline film was improved.
INTRODUCTION
Recently, we have studied on hydro-thermally synthesis of PZT piezoelectric polycrystalline thick film on titanium (Ti) substrates[1], and developed ultrasound sensors[2],[3] by using the PZT hydrothermal polycrystalline thick film (PZT-HPTF) on Ti substrate. Ohba et al had studied actively on deposition of PZT film by hydrothermal method[4]-[6]. However, they did not study on the application for the ultrasound sensor. Deposition of PZT-HPTF has the advantages like needless of sintering process, annealing process, polling process etc[7]. PZT-HPTF can be deposited on the Ti substrate with complex shape or tiny shape. On the other hand, PZT-HPTF has disadvantages like unstable material properties, low piezoelectric constants, rough surface of the film, existence of many pinholes, low dielectric breakdown electric field etc. The purpose of this study is resolving above problems in order to apply PZT-HPTF to the ultra-miniature high frequency medical ultrasound array probe like intra vascular ultrasound probe (IVUS probe). The ultra-miniature high frequency medical ultrasound probe should have many extremely tiny piezoelectric elements. PZT piezoelectric ceramics or polymer piezoelectric films like PVDF were
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employed. There was the problem like low yield rate for production of the ultrasound probe with such tiny piezoelectric elements. We think PZT-HPTF is ideal piezoelectric material except above disadvantage for the high frequency tiny ultrasound
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