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$Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ 계 완화형 강유전체의 특성에 미치는 $PbTiO_3$ 첨가량의 변화 -I.유전특성 및 초전특성-
박재환,흥국선,박순자 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.4
PMN계에서 유전적 성질에 관한 연구들은 광범위하게 이루어져 왔으나 전계인가 변위특성에 관한 폭넓은 연구는 매우 드물다. 본 연구에서는 완화형 강유전체의 가장 대표적인 PMN계에서 PT의 함량 및 측정 온도의 변화에 따른 유전적 성질 및 전계인가 변위특성을 광범위하게 조사하는 것을 목표로 하고 있다. 전형적인 columbite precur-sor법에 의해 분말을 준비하고 고상소결방법에 의하여 모든 시편을 제조하였다. PT의 함량이 증가하면서 직선적으로 (T$\varepsilon$max)가 증가하였으며 유전율은 13000~22000 사이의 값을 보였다. 유전율의 온도 의존성은 PMN의 경우 전형적인 완화형 강유전체의 유전 특성을 보이지만 PT의 함량이 증가될수록 보통 강유전체의 sharp한 거동을 보였다. 전계인가 변위특성에서는 단순히 유전율이 최대가 되는 온도에서 발생 strain이 최대가 되는 것은 아니며 tetragonal-cubic의 phase transition에서는 strain의 증가가 없고 rhombohedral에서 tetragonal 혹은 rhombohed-ral에서 cubic으로의 상전이에서만 strain이 크게 나타남을 알 수 있었다. In order to understand the electrostrictive behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) solid solutions the dielectric constants and the electric-field-induced strains in (1-x)PMN-xPT (x=0.0-0.4) were investigated in the temperature range -5$0^{\circ}C$-20$0^{\circ}C$. Powder of (1-x)Pb(Mg2/3Nb2/3)O3-xPbTiO3 (x=0.0, 0.1, 0.2, 0.3, 0.35, and 0.4) were prepared from the oxide forms of Pb, Mg, Nb and Ti via a columbite precursor method As the amount of PbTiO3 increases the temperature of maximum dielectric constant(T$\varepsilon$max) increases and the phase transition become less diffusive. The strain maximum occurs only when the diffuse phase transition occurs from rhombohedral to cubic or rhombohedral to tetragonal as in x=0.1-0.35 The strains monotonically decrease with temperature in the materials in which phase transition occurs from tetragonal to cubic as in x=0.4.
$Li_2O-Al_2O_3-Ta_2O_5$ 삼성분계에 있어 $LiTaO_3$ 고용체의 구조 및 특성에 관한 연구
김정돈,흥국선,주기태 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.4
The partial substitution of LiTaO3 with Al2O3 caused the variation of dielectric properties and a lower melting temperature yielding an easier growth of single crystal. The lattice constants and Raman band broadening were measured for the LiTaO3 solid solution in which the cations of Li+ and Ta5+ were partially substituted by Al3+ cation. The LiTaO3 type limit phases were obtained. ; Li1.15Al0.45Ta0.7O3 for cationic excess Li1.15Al0.45Ta0.7O3 for stoichiometry Li0.85Al0.05TaO3 for cationic deficit. The second phase was formed beyond the solubility limit. The limit phase (Li0.85Al0.05TaO3) in the region of cationic deficit showed the lowest Cuire temperature of 61$0^{\circ}C$ and melting point of 152$0^{\circ}C$ compared to the solid solutions in other regions (TMp=1$650^{\circ}C$, Tc=69$0^{\circ}C$ for LiTaO3)
$Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$계 완화형 강유전체의 특성에 미치는 PbTiO3 첨가량의 영향 -II. 상전이 및 전계인가 변위특성-
박재환,김인태,김동영,조서용,흥국선,박순자 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.5
In order to understand the electrostrictive behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solutions the dielectric constants the electric-field-induced strains and the pyroelectric coefficients of (1-x)PMN-xPT (x=0.1-0.4) were investigated in the temperature range -50~20$0^{\circ}C$. For x=0.1~0.35 where the phase transi-tion is diffusive the strain has a maxima at the temperature of maximum pyroelectric coefficient (depolrizing temperature) rather than the temperature of maximum dielectric constant. For x=0.4 where the phase transition is relatively sharp the strain decreases monotonically as the temperature increases. Relationships among the above experimental results are discussed.
오흥국,남궁인 亞洲大學校 1983 論文集 Vol.6 No.-
This study is concerned with hot forging of sintered porous metal ring with inner barrier. It is analyzed by Upper Bound approach for finding the normalized forging pressure at various relative densities and shape factors of the test specimens. Experiments are carried out for sintered porous ring, which were compacted with the powders Fe95 + Cu5, Fe90 + Cu10 and Fe47.5 + Cast iron cutting chip powder 47.5 + Cu5. The specimens are heated in the furnace at 1100℃ and then forged in the preheated die at 200℃. The experimental and the analytical results are compared. Possible explanations for the observed effects are discussed.