Electric Modulus Scaling Behaviors of the Near Stoichiometric Potassium Lithium Niobate Crystal

전병억,최병춘,Chang-Hoon Kim,김형국,배종성,정중현,황윤회 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III

An electric modulus analysis was adapted in the low-frequency range from 100 Hz to 1 MHz for the near-stoichiometric potassium lithium niobate (K2.83Li1.84Nb5.33O15.66, KLN43) crystal. KLN43 displayed relaxor-like dielectric behaviors at temperatures around the dielectric maximum temperature Tmax 510 C. The corresponding minima of the real and the imaginary electric moduli M0(!) and M00(!) were observed at Tmax. Dispersive behaviors of the electric modulus were observed at the temperatures below and above Tmax. At temperatures lower and higher than Tmax, the frequency-dependent imaginary modulus showed a distinct peak that collapsed into a master curve. During the diffused phase transition, there were two imaginary modulus relaxation mechanisms. The maximum angular frequency !max of the imaginary electric modulus followed the Arrhenius law. The activation energies at temperatures lower and higher than Tmax were 0.56 eV and 1.57 eV, respectively. The superposition of the two imaginary modulus peaks during the diffused phase transition of KLN43 was assumed to be due to the hopping conduction of the mobile charge carriers and/or to the rotational dielectric relaxation mechanism.bt5bt

Thermal Evolutions of the Domain Walls in a BaTiO3 Nanoparticle

전병억,문병기,김진수,정중현,최병춘,정수태,Yong Il Kim,Kwon-Sang Ryu 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

Direct observations of domain walls by using transmission electron microscope were applied to BaTiO3 (BT) nanoparticles synthesized by using the solvothermal reaction method. Many BT nanoparticles with domains were observed, and the domain walls were 2-4 nm in width and appeared to be parallel to the (111) planes. The thermal evolutions of the domain walls of the about 25-nmsized BT particle were confirmed by using in-situ high voltage electron microscopy at temperatures from RT to 200 ˚C. The (110) and (001)/(002) planes appeared in the domains, and the domain walls with a 3-nm width were parallel to the (111) plane. As the temperature increased, the area of the domains increased, and the domain walls became narrower. The domain walls re-widened at the same position and the same area when cooled down to room temperature.

The Ionic Conduction and Dielectric Properties of Pure and Na-Doped K3Li2..xNb5+xO15+2x Crystals

전병억,Yoon-Hwae Hwang,Chung Sik Kim,Dong Jin Kim,Gwang Soo Jeen,Hyung Kook Kim,Jung Nam Kim,Suk Chul Song 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV

Pure and Na-doped potassium lithium niobates (KLN) crystals were grown by r.f. heating Czochralski method from the melts composition Na2O : K2O : Li2O : Nb2O5 = x : 32 - x : 25 : 43 (x = 0, 2 mol%). Tetragonal cell volume of the Na-doped KLN crystal decreases compare to the pure KLN, because K+ ions in the A1 sites were partially replaced by Na+ ions. The ferroelectric phase transition was observed from the dielectric properties along the polar c-axis of pure and Na-doped KLN crystals. The Curie temperature of pure and Na-doped KLN were 502 C and 456 C, respectively. Both KLN crystals showed the strong low frequency dielectric dispersion at about phase transition temperatures in the frequency range of 100 Hz 10 kHz. The ac conductivity showed a slope change at the Curie temperature in the Arrhenius plot of log(kBT33) vs. 103=T . The electrical conduction in pure and Na-doped KLN crystals originates mainly from the ionic hopping. The Li+ ions in A1 sites are considered to be the main charge carriers. The activation energy at lower temperature of pure and Na-dope KLN were 0.83 eV and 0.72 eV, respectively.

Diffused Phase Transition of Ba1−xEuxTiO3 Ceramics

전병억,최병춘,정중현,문병기 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12

By applying the sol-gel method, we fabricated Ba1−xEuxTiO3 (BET) ceramics as a single peroveskite phase in the composition range of x = 0 0.20. The BET ceramics displayed a ferroelectric phase transition temperature that changed from 120 C to 80 C, and exhibited the coexistance of the tetragonal, and cubic structures as the Eu composition was increased. They also displayed anomalous dielectric behaviors related to structural relaxation in the temperature range from 200 C to 600 C. We considered the Arrhenius temperature dependence of the dielectric relaxation time by using the electric modulus formalism. The characteristic activation energy was thought to be related with the substitution of Eu (Eu2+, Eu3+) ions for Ba2+ or Ti4+ ions in the perovskite structure.

Ferroelectric Phase Transitions in (1-x)K_0.5Na_0.5NbO₃-(x/5)K₂NaLi₂Nb₅O₁₅ Composite Ceramics

전병억,최병춘 한국물리학회 2012 새물리 Vol.62 No.1

Lead-free dielectric and piezoelectric composite ceramics were considered as a mixture of multiple phases coexisting in the alkaline niobates ANbO_3 (A = K, Li and Na). ANbO_3displayed perovskite, completely filled tetragonal tungsten-bronze,LiNbO_3, and other structures in the ternary system of KNbO_3-LiNbO_3-NaNbO_3. The respective phases had different melting points and corner sharing oxygen octahedra of NbO_6. In this report, the composite K_0.5Na0.5NbO_3 (KNN) and K_2NaLi_2Nb_5O_15 (KNLN) ceramics, textiti.e.,(1-x)KNN-(x/5)NKLN (x = 0 - 0.1) ceramics, were confirmed to show a composition dependence of the structural phase transition temperature, T_T-O, from the tetragonal to the orthorhombic structure.

캔위성 발사위치 회귀를 위한 패러글라이딩 제어 및 고도별 이산화탄소 농도 측정

전병억(Byeongeog Jun),김민권(MInGwon Kim),이상벽(Sangbyuk Lee),임도현(Dohyun Lim) 한국항공우주학회 2022 한국항공우주학회 학술발표회 논문집 Vol.2022 No.11

Optical and Electrical Properties of Li-Doped ZnO Thin Films by the Pulsed Laser Deposition

최병춘,전병억,김유성,문병기,정중현,Haeyoung Choi,김정환,이성수,배종성 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

We studied the effects of Li incorporation on the physical properties of ZnO thin films, which is comparable to native defects in the ZnO. The Li-doped ZnO (ZnO:Li) thin films were grown on Al(0001) substrates by using the pulsed laser deposition method. The targets employed were high-purity ZnO ceramics with different Li contents: Li 0.05 at.%, Li2O 0.05 mol% and Li 0.10 at.%. We observed that the optical and the electrical properties of the ZnO:Li thin films depended on the Li concentration. The crystalline qualities and the surface morphologies of the thin films were studied by using X-ray diffraction and scanning probe microscope image. The thicknesses of the ZnO:Li thin films were estimated by using the interference patterns of the optical transmittance data. In order to investigate the potential transparent conductive applications of the ZnO:Li thin films, we discuss the photoluminescence and the Hall conductivity. Consequently, ZnO:Li thin lms are expected to be almost epitaxially grown on Al2O3 (0001) substrate and exhibits n-type conductivity at room temperature.

Acoustic Anomalies of Potassium Lithium Niobate Single Crystals near the Ferroelectric Phase Transition Temperature

고재현,전병억,황윤홰,Do Han Kim,Seiji Kojima 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2

The acoustic properties of two potassium lithium niobate single crystals have been investigated by using Brillouin spectroscopy. The temperature dependence of the Brillouin shifts corresponding to two elastic constants, C11 and C33, was obtained over a wide temperature range including the phase transition temperature (Tc). Consistent with the uniaxial nature of the tetragonal tungsten- bronze structure and the Ising-type order parameter along the c-axis, only the C33 showed a large acoustic anomaly at Tc while C11 did not show a substantial change in both crystals. This result indicates that the longitudinal acoustic wave propagating along the polar direction couples strongly to the order parameter fluctuations, resulting in a significant softening of C33, as well as a substantial increase in the acoustic damping in the paraelectric phase. Changes in the acoustic properties above Tc have been partly ascribed to the electrostrictive coupling between the strain and the squared order parameter of polar nanoregions and fluctuation damping, which seem to be correlated with the diffuse nature of the ferroelectric phase transition observed in the present study. However, another microscopic origin seems to contribute to the softening of C33 at temperatures above Tc, which is unclear at present.

증착 조건이 KLN 박막의 형상에 미치는 영향

박성근,전병억,김진수,김지현,최병진,남기홍,류기홍,김기완,Park, Seong-Geun,Jeon, Byeong-Eok,Kim, Jin-Su,Kim, Ji-Hyeon,Choe, Byeong-Jin,Nam, Gi-Hong,Ryu, Gi-Hong,Kim, Gi-Wan 한국재료학회 2001 한국재료학회지 Vol.11 No.1

The growth characteristics of 4-fold grain which was appeared in KLN deposition on $Pt/Ti/SiO_2/Si(100)$ substrate was studied by varying process variables. Substrate temperature, sputtering pressure, rf power were selected as process variables, and experiment was carried out near optimum fabrication condition. When using K and Li enriched target, the optimum fabrication conditions were substrate temperature of $600^{\circ}C$, sputtering pressure of 150mTorr, rf power of 100 W and its surface morphology is sensitively varied by small deposition condition changes. KLN is composed of elements which have large difference of boiling point. And it is difficult to fabricate thin film at high temperature and high vacuum deposition condition. Furthermore the phenomenon during deposition process can not be explained by using Thorton's model which explains the relation between thin film structure and melting point of thin film materials. These phenomenon can be explained using boiling point of elements which consist of thin film material. 본 실험에서는 $Pt/Ti/SiO_2/Si(100)$ 기판 위에 KLN 박막을 형성할 때 나타나는 4-fold 그레인의 성장 특성을 조사하기 위하여 공정 변수를 변화시키면서 박막을 제작하였다. 공정 변수는 기판 온도, 스퍼터링 압력, 고주파 전력을 선택하여 최적의 증착 조건 근방에서 공정 변수를 변화시키면서 실험하였다. K와 Li가 과량된 타겟을 사용하여 KLN 박막을 제조할 때 최적의 성장 조건은 고주파 전력 100 W, 공정압력 150 mTorr, 기판온도 $600^{\circ}C$이며 공정변수의 작은 변화에도 박막의 표면 형상은 매우 민감하게 변화하였다. KLN은 화합물을 구성하는 원소 사이의 증기화 온도의 차이가 많이나는 물질로서 고온 고진공의 환경에서 박막을 제조할 때 어려움이 있으며, 녹는점과 기판 온도와의 관계를 설명한 Thornton의 모델로 설명하기 어려운 현상이 나타났다. 이러한 것은 박막 물질을 이루는 구성 원소의 증기화 온도를 이용하여 이 현상을 간단하게 설명할 수 있었다.

Dielectric and Ferroelectric Properties of EuxBa1-xTiO3 Fine Ceramics

최병춘,전병억,김은지,김유성,김진수,문병기,Jung Hyun Jeong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

EuxBa1-xTiO3 (EBT, x = 0.01 ∽ 0.1) fine ceramics were prepared from EBT nanoparticles, where the sol-gel method was employed to substitute Eu homogeneously for Ba in the BaTiO3. With calcining and sintering the EBT nanoparticles, the grain sizes of EBT fine ceramics were measured to be about 0.1 ∽ 1.0 μm by using scanning electron microscopy. The EBT fine ceramics exhibited the ferroelectric D-E hysteresis. The Curie temperature shifted toward 70 ℃ for EBT (x = 0.10) fine ceramics and displayed diffuse phase-transition behaviors. The Curie temperature of EBT is thought to be lowered by the incorporation of Eu ions, where Eu substituted for Ba in the A sites of BaTiO3. EuxBa1-xTiO3 (EBT, x = 0.01 ∽ 0.1) fine ceramics were prepared from EBT nanoparticles, where the sol-gel method was employed to substitute Eu homogeneously for Ba in the BaTiO3. With calcining and sintering the EBT nanoparticles, the grain sizes of EBT fine ceramics were measured to be about 0.1 ∽ 1.0 μm by using scanning electron microscopy. The EBT fine ceramics exhibited the ferroelectric D-E hysteresis. The Curie temperature shifted toward 70 ℃ for EBT (x = 0.10) fine ceramics and displayed diffuse phase-transition behaviors. The Curie temperature of EBT is thought to be lowered by the incorporation of Eu ions, where Eu substituted for Ba in the A sites of BaTiO3.