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오유영,이광섭,Masao Kamiko,고중혁 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.2
A lead-free piezoelectric ceramic, (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (hereafter (1-x)BZT-xBCT), was investigated for functional device applications. Lead-free piezoelectric materials with high piezoelectric charge coefficients and voltage coefficients are indispensable for functional industrial applications. Piezoelectric ceramic specimens tend to shrink in size during the sintering process without melting. This study focused on this phenomenon as a unique characteristic of piezoelectric ceramic materials, and derived the materials’ activation energies from this phenomenon, employing the Arrhenius relationship. Then the estimated activation energy was employed to determine the relationship between the piezoelectric properties and crystalline properties, while varying sintering temperature and chemical stoichiometric composition. Piezoelectric properties can change depending on the sintering temperature and process conditions. Crystalline properties and piezoelectric properties can be influenced by the sintering temperature and holding times. In this research, sintering temperature dependent structural and dielectric properties were investigated. (1-x)BZT-xBCT ceramics showed the highest piezoelectric coefficient of 470 pC/N. Sintering temperature dependent shrinkage rate and activation energy were estimated and calculated for the various sintering processes. In this research, two different activation energies for the shrinkage process were estimated.
Defects controlled stress engineering in Al-doped ZnO transparent multilayered thin films
Kang Jihye,Yun Jaeyong,Oh Yoo-Young,Kim Sung-Jin,Kamiko Masao,Kim Nam-Hoon,Koh Jung-Hyuk 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.5
This study explores stress engineering in multilayered structures of Al-doped ZnO thin films by controlling defects in them. Al-doped ZnO thin films are examples of transparent conducting oxides. Owing to their high conductivity and transparency, Al-doped ZnO thin films have various promising applications. However, defects and dislocations in thin films can deteriorate their electrical and optical properties. These defects or dislocations can be formed during the thin-film deposition process. Especially, defects can be formed between the layers during the stacking process of the sol–gel method. Therefore, methods to control defects have been designed and simulated to engineer stress in thin films. In this study, layered Al-doped ZnO thin films with different thicknesses were prepared to investigate the interface effects and electron motion in them.