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Bi 과잉에 따른 BiFeO<sub>3</sub>-BaTiO<sub>3</sub> 세라믹스의 압전 및 유전특성
이재홍,이명환,송태권,김원정,성연수,김명호,Lee, Jae Hong,Lee, Myang Hwan,Song, Tae Kwon,Kim, Won-Jeong,Sung, Yeon Soo,Kim, Myong-Ho 한국재료학회 2017 한국재료학회지 Vol.27 No.3
The effects of an excess of Bi on the piezoelectric and dielectric properties of $0.60Bi_{1+x}FeO_3-0.40BaTiO_3$ (x = 0, 0.01, 0.03, 0.05, 0.07) were investigated. The ceramics were processed through a conventional solid state reaction method and then quenched after sintering at different temperatures in the range of $980{\sim}1070^{\circ}C$. A single perovskite structure without any secondary phase was confirmed for all compositions and temperatures. It was found that excess Bi reduced the sintering temperatures, acted as a sintering aid and enhanced the properties in combination with quenching. Curie temperature ($T_C$) was found to slightly increase due to the presence of excess Bi; electrical properties were also improved by quenching. At x = 0.03 and $1030^{\circ}C$, remnant polarization ($2P_r$) was as high as $45.4{\mu}C/cm^2$ and strain at 40 kV/cm was up to 0.176 %.
비납계 Bi<sub>0.5</sub>Na<sub>0.5</sub>의 강유전 및 압전 특성에 미치는 Nb-doping 효과
여홍구,성연수,송태권,조종호,정순종,송재성,김명호,Yeo, Hong-Goo,Sung, Yeon-Soo,Song, Tae-Kwon,Cho, Jong-Ho,Jeong, Soon-Jong,Song, Jae-Sung,Kim, Myong-Ho 한국재료학회 2006 한국재료학회지 Vol.16 No.11
Nb was doped to Pb-free $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) by a solid state mixing process to form $(Bi_{0.5}Na_{0.5})Ti_{1-x}Nb_xO_3\;(x=0{\sim}0.05)$ (BNTNb) and its doping effects on ferroelectric and piezoelctric properties of BNT were investigated. The BNTNb solid solutions were formed up to x=0.01 with no apparent second phases while grain sizes decreased. As x increased, coercive field ($E_c$) and mechanical quality factor ($Q_m$) decreased but piezoelectric constant ($d_{33}$) increased, which indicates Nb acts as a donor for BNT.
BaO 과잉량에 따른 BaTiO<sub>3</sub>의 전기전도도
여홍구,국민호,김명호,송태권,배동식,박태곤,이순일,Yeo, Hong-Goo,Kuk, Min-Ho,Kim, Myong-Ho,Song, Tae-Kwon,Bae, Dong-Sik,Park, Tne-Gone,Lee, Soon-Il,Randall, Clive A. 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.5
In this study the electrical conductivity of excess BaO in $BaTiO_3$ was measured to investigate the relationship between defects and solubility in the temperature range of $900^{\circ}C$ to $1300^{\circ}C$ under various oxygen partial pressure. First of all, quenched $BaTiO_3$ powders of various Ba/Ti ratios were analysed by X-ray diffraction to confirm whether second phase is formed or not. As the results, we observed the solubility of BaO in the temperature range of $1200^{\circ}C$ to $1400^{\circ}C$, and it was also found that the conductivity minima move to lower $PO_2$ with increasing excess BaO within solubility limit.
비납계 (Bi<sub>0.5</sub>Na<sub>0.5</sub>)TiO<sub>3</sub>-BaTiO<sub>3</sub> 강유전 세라믹 재료의 유전 및 압전 특성
국민호,김명호,조정아,성연수,송태권,배동식,정순종,송재성,Kuk Min-Ho,Kim Myong-Ho,Cho Jung-A,Sung Yeon-Soo,Song Tae Kwon,Bae Dong-Sik,Jeong Soon-Jong,Song Jae-Sung 한국재료학회 2005 한국재료학회지 Vol.15 No.11
The structural, piezoelectric and ferroelectric properties of $(1-x)(Bi_{0.5}Na_{0.5})TiO_3$ x=0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) ceramics were investigated. A gradual change in the crystal and microstructures with tile increase of $BaTiO_3$ (BT) concentration was observed. The $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) samples show unusual properties as ferroelectric relaxer materials. We observed a phase transition in BNT solid solutions with BT having normal ferroelectric phase transition. At room temperature, BNT presents a single phase without the morphotropic phase boundary (MPB). In the case of samples doped with $4\~8 mol\%$ BT, rhombohedral-tetragonal MPB was formed and the piezoelectric properties were improved.
이정훈,류경현,성연수,조종호,송태권,김명호,Lee, Jung-Hoon,Ryu, Gyung-Hyun,Sung, Yeon-Soo,Cho, Jong-Ho,Song, Tae-Kwon,Kim, Myong-Ho 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.5
Pb(Zr,Ti)$O_3$ (PZT) based ceramics with superior piezoelectric properties have been extensively used in various domestic and industrial appliances. However, PZT ceramics causing environmental contamination and health problems need to be eventually replaced by any of Pb-free materials. $(Na_{0.53}K_{0.47})(Nb_{1-x}Ta_x)O_3$ (NKNT), one of Pb-free piezoelectric ceramics, has long been known but its properties are not fully understood and developed. In this study, dielectric and piezoelectric properties of Pb-free NKNT ceramics were studied with Ta substitution for B-site at x = 0~0.6. It was found that polymorphic phase transition (PPT) between orthorhombic and tetragonal phases was notably influenced by Ta substitution. The highest piezoelectric coefficient ($d_{33}$) of 284 pC/N was occurred at x = 0.45.
비납계 (Bi<sub>0.5</sub>Na<sub>0.5</sub>)<sub>(1-x)</sub>Ba<sub>x</sub>TiO<sub>3</sub> 압전 세라믹 재료의 최적 조성
성연수,여홍구,조종호,송태권,정순종,송재성,김명호,Sung, Yeon-Soo,Yeo, Hong-Goo,Cho, Jong-Ho,Song, Tae-Kwon,Jeong, Soon-Jong,Song, Jae-Sung,Kim, Myong-Ho 한국재료학회 2007 한국재료학회지 Vol.17 No.2
Optimum compositions for piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics were investigated in the range of $x=0{\sim}0.1$ covering rhombohedral to tetragonal phase regions. No impurity phases other than a perovskite phase were found and the grain size decreased with increasing x. A two-phase coexisting morphotropic phase area rather than boundary dividing rhombohedral and tetragonal phase regions appeared to exist at $x=0.05{\sim}0.08$. As for piezoelectric properties within morphotropic phase compositions, the piezoelectric constant ($d_{33}$) and the electromechanical coupling factor ($K_p$) showed peak values at x=0.065, 192 pC/N and 34%, respectively, indicating x=0.065 as an optimum composition for piezoelectric $(Bi_{0.5}Na_{0.5})_{(1-x)}Ba_xTiO_3$ ceramics.