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$BaTiO_3$의 강유전-상유전 상전이에 미치는 A($Cu_{1/3}Nb_{2/3}$)$O_3$ (A=Pb, Ba 및 Sr)의 영향
박휴범,김정,김시중,Park, Hyu-Bum,Kim, Jung,Kim, Si-Joong 한국세라믹학회 1991 한국세라믹학회지 Vol.28 No.12
The influences of A(Cu1/3Nb2/3)O3(A=Pb, Ba and Sr) on the ferroelectric-paraelectric phase transition of BaTiO3 ceramics has been investigated. The tetragonality of crystal structure decreased with increasing A(Cu1/3Nb2/3)O3 content at room temperature. A linear correlation between Curie point and the tetragonality of lattice was not observed. In all three systems the variation of Curie point with the mole fraction showed similar tendency that the Curie point decreased at lower mole fraction but gradually increased in the region of higher mole fractions, Diffuse phase transitions were observed at higher mole fractions. The variation of Curie points could be explained by internal stress and Jahn-Teller distortion of BO6 due to Cu2+, and it was thought that the diffuse character of phase transition was caused by compositional fluctuation.
Poly(vinyl alcohol) 을 이용한 변형된 졸-겔형 반응에 의한 ??의 합성
국승택,김건,박동곤,남상성,권호진,박휴범 숙명여자대학교 자연과학연구소 1995 자연과학논문집 Vol.- No.6
LaMNO₃나 LaCoO₃와 같은 perovskite 결정구조를 갖는 복합산화물들은 산화-환원 촉매제나 고온에서의 전극물질로서 유용하게 쓰이는 물질들이다. 이와 같은 복합산화물들은 성분 금속의 금속산화물들을 혼합하여 1000℃ 이상의 높은 온도에서 장시간에 걸쳐서 가열하는 전통적인 고상반응(solid state reaction)을 통하여 합성할 수 있다. 고온에서의 가열과정을 통하여 합성된 perovskite들은 매우 낮은 표면적을 가지고 있기 때문에 표면의 촉매능이 크게 감소되어 있다. 이러한 고온에서의 가열과정은 불균일한 조성에서 비롯되는 diffusion barrier를 극복하기 위하여 요구되는 과정이다. 이와같은 diffusion barrier를 최소화하기 위하여 두가지 다른 방법을 적용할 수 있다. 한가지 방법은 고체반응물의 입자크기를 줄여서 불균일한 영역의 크기를 작게하고 입자들간의 접촉면적을 최대화하는 방법으로서, 구성 금속성분의 금속 아세트산염이나 질산염을 사용하여 공침법에 의해 얻어지는 미세한 입자들을 전구체(precursor)로 사용하는 방법을 들 수 있다.
La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조
김정수,박휴범,안태호,김시중,Kim, Jeong Su,Park, Hyu Beom,An, Tae Ho,Kim, Si Jung 대한화학회 1994 대한화학회지 Vol.38 No.4
La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조와 단일상 영역을 X-선 회절분석기와 주사전자현미경을 사용하여 연구하였다. La$_2O_3$-변형 BaTi$O_3$의 안정한 결함구조는 La$^{3+}$ 이온이 격자구조내의 Ba$^{3+}$ 이온을 치환하고 Ti빈자리가 전하 불균형을 보상하기 위한 결함으로 생성된 [($Ba^x_{Ba})_{1-2x}(La{\cdot}_{Ba})_{2x}][Ti^x_{Ti})_{1-x/2}(V""_{Ti})_{x/2}]O_3$이다. 안정한 결함구조가 형성되도록 BaTi$O_3$에 La$_2O_3{\cdot}3/2TiO_3$를 혼입할 때 단위격자는 약 3 mol%가 혼입될 때부터 정방정에서 입방정으로 변하였고, 고용한계는 약 14 mol%이었다. La2$O_3{\cdot}3/2TiO_2$를 고용한계 이상으로 혼입할 때는 이차상으로 La_4Ba_2Ti_5O){18}$가 생성되었다. La$_2O_3$-변형 BaTi$O_3$ 조성에서 BaO가 과량 존재하면 소결성이 나쁘지만, Ti$O_2$가 과량으로 존재하면 액상소결에 의하여 소결성이 좋아짐을 확인할 수 있다. The stable defect structure and the single phase region of La$_2O_3$-modified BaTi$O_3$ have been studied by X-ray diffractometer and scanning electron microscope. The stable defect structure of La$_2O_3$-modified BaTi$O_3$ has been identified as [($Ba^x_{Ba})_{1-2x}(La{\cdot}_{Ba})_{2x}][Ti^x_{Ti})_{1-x/2}(V""_{Ti})_{x/2}]O_3$ which consists of La$^{3+}$ ion substitution for Ba$^{3+}$ ion in the lattice structure and the formation of Ti vacancies for the charge compensation. When 3 mol% of La$_2O_3{\cdot}3/2TiO_3$ was added to BaTi$O_3$, the unit cell structure was transformed from tetragonal to cubic and the solubility limit was about 14 mol%. When La$_2O_3{\cdot}3/2TiO_2$ was added above this solubility limit, the second phase, La$_4Ba_2Ti_5O_{18}$, was formed. In the La$_2O_3$-modified BaTi$O_3$, it was found by the liquid phase sintering process that the sinterability was decreased by excess BaO but increased by excess Ti$O_2$.
$Na^+/La^{3+}$이온으로 치환된$Pb(Mg_{1}{3}Nb_{2}{3})O_3$의 구조 변화 및 유전 성질
홍영식,박휴범,안태호,김시중,Hong, Young-Sik,Park, Hyu-Bum,Ahn, Tae-Ho,Kim, Si-Joong 대한화학회 1996 대한화학회지 Vol.40 No.9
$ABO_3$계 perovskite 구조에서 A자리의 $Pb^{2+}$ 이온이 $Na^+La^{3+}$혼합 이온 으로 0-50mol.%치환된 $Pb_{1-x}(Na_12/La_12)_x(Mg_13/Nb_23/)O_3$ 화합물의 구조변화와 유전 성질을 X-선 회절법, 작외선과 라만 분광법, LCR meter등으로 연구하였다. $Na^+La^{3+}$혼합 이온의 치환량과 소결 온도가 증가함에 따라 perovskite 상의 양이 증가하였다. 치환량이 증가할 때 1:1 질서화에 의한 초격자선을 X-선 회절법으로 발견할수 없었지만, 라만 분광법과 이완성 매개변수의 증가로부터 A자리 양이온의 크기감소가 질서화에 영향을 미침을 알 수 있었다. Pb_{1-x}(Na_12/La_12)_x(Mg_13/Nb_23/)O_3$의 유전 성질은 perovskite 상의 양과 낟알 크기 및 밀도에 의해 영향을 받았고, 치환량이 증가할 때 상전이는 확산되었으며 상전이 온도는 감소하였다. The structural changes and dielectric properties of Pb1-x(Na1/2La1/2)x(Mg1/3Nb2/3)O3 compounds substituted by 0∼50 mol.% of Na+/La3+ mixed ions were investigated by X-ray diffraction method, IR and Raman spectroscopy, and LCR meter. The amount of perovskite phase increased with the increases of Na+/La3+ substituents and sintering temperatures. Although the superlattice lines due to 1:1 ordering were not detected by X-ray diffraction method, it was found, from the Raman spectroscopy and the increase of diffuseness coefficient, that the ordering behavior was related to the decrease of A site ion size. Dielectric properties in Pb1-x(Na1/2La1/2)x(Mg1/3Nb2/3)O3 were affected by the amount of perovskite phase, grain size, and density. The phase transitions were broadened and phase transition temperatures were lowered by the increase of Na+/La3+ ions.
N₂O₃계 거대고리 리간드와 전이금속 이온과의 착물 형성에 관한 연구
최규성,박휴범,유한준 慶南大學校 附設 基礎科學硏究所 1992 硏究論文集 Vol.4 No.-
The stability constants of the complexes of transition metal ions(Co²+, Ni²+, Cu²+, and Zu²+) with N₂O₃-donor macrocyclic lignads such as 1,15-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacy-cloheptadecane(NenOdienH₄)and 1,15-diaza-3,4 :12, 13-dibenzo-5, 8, 11-trioxacyclooctade-cane( NtnOdieH₄)have been determined by polarographic method in MeOH solution at 25℃. From the results, the followings have been obstained, 1. In MeOH solution, transition metal ions from a 1:1 complex with these ligands. 2. The order complex stability constants of transition metal ions these ligands is Co(II) < Ni(II) <Cu(II) < Zn(II), the same as the natural order of stability proposed by Williams-Irving. 3. The order of stability constants of Ni(II), Cu(II) ions is NenOdienH₄> NtnOdienH₄, of Co(II), Zn(II) ions is NenOdienH₄< NtnOdienH₄.
Nd, La, K, Na이 치환된 $Pb(Mg_{1/3}Nb_{2/3})O_3$ 세라믹의 구조 및 유전 성질에 관한 연구
권숙화,박휴범,김정,홍영식,김시중,Kweon, Sook-Hwa,Park, Hyu-Bum,Kim, Jeong,Hong, Young-Sik,Kim, Si-Joong 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.7
The structural and dielectric properties of Pb(Mg1/3Nb2/3)O3 ceramics substituted by Nd3+, La3+, K+ and Na+ were studied over 0~50 at.% substituent content. The 1 : 1 ordering behavior of Mg2+ and Nb5+ ions in the B site sublattice was observed in Nd3+-and La3+-modified compounds. The degree of ordering was increased with Nd3+, La3+ content in the compounds. But K+-or Na+-modified compounds did not exhibit the ordering behavior. This was explained by charge and size effect of A and B site cations and oxygen vacancies. As the mole fractions of substituent increased, the maximum values of dielectric constants were rapidly decreased and the phase transitions were broadened. Phase transition temperature was correlated with the covalency of A-O and B-O bonding.
전하소법으로 합성한 $(1-x)Pb(Fe_{1/2}Nb_{1/2})O_3-xPbTiO_3$의 구조와 유전성질에 대한 연구
홍영식,박휴범,김정,김건,김시중,Hong, Young-Sik,Park, Hyu-Bum,Kim, Jeong,Kim, Keon,Kim, Si-Joong 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.11
Pb(Fe1/2Nb1/2)O3 and (1-x)Pb(Fe1/2Nb1/2)O3-xPbTiO3 ceramics were prepared by the precalcination method. Their structural and dielectric properties were investigated. The amount of perovsikte phase was increased by the precalcination and the dielectric properties of ceramics were improved. Additions of PbTiO3 were found to increase the tetragonality (c/a) of crystal lattice and Tc. In the middle region of (1-x)Pb(Fe1/2Nb1/2)O3-xPbTiO3, duffuse phase transitions (DPT) were observed.
$(1-y)Pb(Mg_{(1-x)/3}Zn_{x/3}Zn_{x/3}Nb_{2/3})O_3-yBaTiO_3$ 세라믹스의 구조 및 유전 성질
홍영식,박휴범,김시중 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.8
Dielectric properties and the stabilization of perovskite phase for the (1-y)Pb(Mg(1-x)/3Znx/3Znx/3Nb2/3)O3-yBaTiO3 ((1-y)PM1-xZxN-yBT) ceramics have been investigated as a function of amount of x and y. In the (1-y)PM0.6Z0.4N-yBT ceramics, the amount of pyrochlore phae was decreased by the addition of 2 mol% BT and the dielectric constant was increased. However, the dielectric constant decreased with further addition of BT even though pyrochlore phase was decreased. Dielectric prooperties in (1-y)PM0.6Z0.4N-yBT ceracmis were affected by the character of the BT rather than the amount of pyrochlore phase. The phase transitions were broadened and phase transition temperatures were lowered by the increase of BT contents.