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EN05.03.04 : Development of Novel 1D Nanostructure for BaTiO3 Piezoelectric Harvesters

5:00 PM–7:00 PM Apr 3, 2018

PCC North, 300 Level, Exhibit Hall C-E

Description
SeonMin Jang1 Moon-hyeok Choi1 Su Chul Yang1

1, Dong-A University, Busan, , Korea (the Republic of)

Kinetic energy harvesters have been extensively studied due to their high-power density given by powerful vibration energy. There are many sources of vibration energy such as human motions, automobiles and other natural motions. For a decade, one dimensional (1D) nanostructures have been widely approached for miniaturization in a piezoelectric field, however, there are still critical limitations of insufficient piezoelectricity and unstable standing on a substrate. In this study, BaTiO3 nanorod bundle arrays as a 1D novel structure were designed to obtain effective piezo-strain change and stable standing on fluorine-doped tin oxide (FTO) glass, simultaneously. In order to develop the nanorod bundle array, TiO2 nanostructures as framework were hydrothermally synthesized with adjusting area density, aspect ratio and free-standing via investigation of pH and precursor effects. It is illustrated that area density was enlarged as an increase in Ti precursor concentration or increase in pH, respectively. Optimum TiO2 nanorod bundle arrays were optimized for non-aggregation of 1D nanostructures on high area density over 60 % with bundle diameter of 100nm consisted of rod diameter of 10nm. Next, M-shaped TiO2 nanorod bundles were developed via chemical etching process to conduct complete phase transformation of BaTiO3. During chemical etching, top surface was found to be more etched compared to side wall because of the higher surface energy of (001) with Z-axis than (110) with X and Y axis. After BaTiO3 phase transformation from the M-shaped nanostructures, conversion ratio was found to be a higher magnitude of 92.3 % compared to 78.4 % conversion ratio of non-etched TiO2 nanostructure. BaTiO3 conversion ratio was defined as follow; Conversion ratio (%) = [XRD peak of BaTiO3] / [XRD peak of TiO2 + XRD peak of BaTiO3] × 100, where the representative peaks of TiO2 and BaTiO3 were shown as (002) at 2θ = 62.8° and (110) at 2θ = 31.3°, respectively. It is noted that the M-shaped nanostructure can offer large diffusion sites of Ba2+ ions determining perovskite (ABO3) phase with high piezoelectricity. The effective BaTiO3 phase conversion using M-shaped nanostructure was confirmed with volume expansion and ion mapping by SEM and STEM analysis, respectively. Finally, the progress of BaTiO3 phase transformation from M-shaped TiO2 nanostructure was confirmed by morphology characterization with variations of Ba2+ ion concentration. During an early stage of phase transformation, BaTiO3 was predominantly formed along Z axis in empty space. As the Ba2+ ion increased, (001) growth along the perpendicular direction to the FTO substrates occurred. On the contrary, (110) growth along X and Y axis hardly occurred owing to low diffusion of the Ba2+ ion. In conclusion, BaTiO3 nanorod bundle structures were successfully synthesized with high conversion ratio, and the novel structure can be a strong candidate for high power piezoelectric devices.

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