Development of bimorph vibrator using lead free BNT piezoelectric film deposited by hydrothermal method
PZT piezoelectric film synthesized hydrothermally has been studied actively in our laboratory. However, it is apprehended recently that PZT affects health and the environment, because PZT is chemical compound containing lead. Therefore, we tried to synthesize lead free BNT piezoelectric film on titanium substrate hydrothermally. The synthesized BNT films on titanium substrates were evaluated with SEM image, XRD pattern and EDS. We fabricated bimorph vibrators with synthesized lead free BNT film and evaluated their performances.
Title Synthesis and Characterization of Piezoelectric ( Bi 1 / 2 Na 1 / 2 ) TiO 3 Films by a Hydrothermal Method
Thin films of lead-free piezoelectric ceramics (Bi1/2Na1/2)TiO3 (abbreviated as BNT) were prepared on pure titanium substrates by a hydrothermal method. The properties of BNT films synthesized from the reaction solution with various contents of bismuth and titanium were investigated using SEM, EDX, XRD and other instruments. Moreover, the effects of the concentrations of starting materials on permittivity and piezoelectric effect of deposited BNT films were discussed. The results showed that an impurity of Bi2O3 crystal was produced on the surfaces of all deposited films. With assumption of deposited films as an system of (1-x) (Bi1/2Na1/2)TiO3-xBi2O3, the BNT content was calculated from the Bi/Ti ratio of the EDX results. The optimized synthesis condition was determined on the evaluation target of the calculated BNT content. In addition, the unimorph cantilever type actuators were fabricated by BNT deposited samples, and their piezoelectric responses were measured at their resonance frequencies under AC field. It was noted that the piezoelectric effect of the deposited BNT film was greatly dependent on its crystallization level.
Hydrothermal synthesis and sintering of electroceramics
The hydrothermal processing of ultrafine Pb 1.88 (Zn 0.3 Nb 1.25 )O 5.305 and Ba(Mg 0.33 Nb 0.67 )O 3 powders as well as their sintering behavior at 1000°C were investigated. The morphological analyses on nanometric powders indicated the presence of mesopores in micrometric agglomerates with open cylindrical pores. High dielectric constants were observed, showing normal frequency dispersion and an intrinsic ac relaxation, relatively masked by low frequency conductivity. The sintered ceramics presented lower dielectric permittivities than the hydrothermal powders, and a classical Cole-Cole plot could be obtained for the Pb 1.88 (Zn 0.3 Nb 1.25 )O 5.305 electroceramic for frequencies above 10 3 Hz.