• 한국세라믹학회지
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• 제45권11호
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• pp.694-700
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• 2008

Proton conducting oxides based on the $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ (M = La, AL) were tested for the alternative electrolyte materials of fuel cell. The power density for single cell of Air |Pt| $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ |Pt| $H_2(3%H_2O)$ system was maximum $0.04W/cm^2$ at $1000^{\circ}C$. In this system, proton transport number was proved to depend on the lattice parameters and the distortion of $CeO_6$ octahedral as a function of the ionic radii of acceptor ions. This proton conducting oxide system requires developing the new electrode materials for application.

• 한국세라믹학회지
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• 제34권8호
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• pp.897-907
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• 1997

Thin films of Bi4-xSmxTi3O12(0$\leq$x$\leq$2) were prepared on Pt/Ti/SiO2/Si(100) at $700^{\circ}C$ using spin-coating with sols derived from Bi-Sm-Ti complex alkoxides. From X-ray diffraction analysis, it was observed that Sm-substituted phases resembled ferroelectric Bi4Ti3O12 in structure. Variations of their lattice parameters depending on the amount of Sm-substitution showed that an anomalous structural distortion might exist at x=1. The grain sizes of the thin films decreased from 0.115 ${\mu}{\textrm}{m}$ to 0.078${\mu}{\textrm}{m}$ with increasing the amount of Sm-substitution. The dielectric constants and the remanent polarizations of the thin films decreased with increasing the amount of the Sm-substitution, which were related to decrease of the stereo-active Bi3+ ion contributing to polarization. However, these values were exceptionally high at x=1, compared to those of the other substituted phases. Such an anomaly suggests that the phase of x=1 has 1:1 chemical ordering between Sm and Bi in structure. The thin films of all compositions except x=2 showed ferroelectricity. The thin film of x=2 was paraelectric, whose grains were too fine to exhibit ferroelectricity.

• Journal of Magnetics
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• 제12권4호
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• pp.137-140
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• 2007

We have studied the temperature dependent magnetic properties and crystalline phase transitionn in small amount Fe doped nickel chromite. The Crystalline structure of $NiCr_{1.7}Fe_{0.3}O_4$ is spinel cubic (Fd-3m) structure with a lattice constant $a_0=8.317\AA$ at room temperature. The magnetic $N\acute{e}el$ temperature $(T_N)$ of the Fe doped nickel chromite sample is determined to be 250 K. The $M\ddot{o}ssbauer$ spectra exhibit that there are two magnetic phases with the two different sites for the $Cr^{3+}$ ions. The spectrum at 4.2 K is fitted to two magnetic components of the magnetic hyperfine fields $H_{hf}=496$ and 485 kOe. From the spectrum at 295 K, the electric quadrupole splittings are observed with large values of 0.49 and 0.50 mm/s, respectively. The values of the isomer shifts at all temperature ranges show that the Fe ions are ferric states. We are suggested that the dynamic Jahn-Teller distortion and anisotropic magnetic relaxation effects due to the crystalline phase transition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.162-162
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• 2013

Magnetic properties of 3d transition metals were determined by exchange interaction between magnetic ions that was characterized by the exchange integral. Bulk Mn material is one of transition metals that have been well known as an anti-ferromagnetic material due to an anti-parallel spin with negative exchange integral. Here we report on the MBE growth of Mn on $BaTiO_3$ (001) substrate and induced ferromagnetism. The bcc ${\alpha}$-Mn single crystal film has been grown on $BaTiO_3$ (100) substrate. The XRD and Raman results indicated that the structural phase transitions of $BaTiO_3$ substrate induced a lattice distortion at the interface. Consequently, the grown Mn film exhibits ferromagnetism with strong saturation magnetization of 495 emu/$cm^3$ at 320 K. The electrical resistivity of the Mn film strongly depended on the crystal structure of $BaTiO_3$ substrate.

• 한국세라믹학회지
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• 제28권12호
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• pp.969-974
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• 1991

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.

• Journal of Magnetics
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• 제12권3호
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• pp.103-107
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• 2007

Magnetic field induced structural transition has been systematically investigated for $La_{1-x}Ba_xMnO_3$ with the fine control of carrier doping $(0.15{\leq}x{\leq}0.20)$. Application of a magnetic field results in the suppression of the rhombohedral-orthorhombic transition temperature $(T_s)$ and the increase of insulator-metal transition temperature $(T_{MI})$. Near x = 0.17, where $T_S$ is similar to $T_{MI}$ at zero magnetic field, we found that the $T_S$ smoothly decreased with magnetic field even though it intersected the $T_{MI}$ near 3 T. Also, the magnetostructural phase diagram obtained from the temperature sweep and from the magnetic field sweep is not significantly modified. By comparing the magnetostructural transition in $La_{1-x}Sr_xMnO_3$, we have suggested that the large disorder originated from ionic size differences between La and Ba may weaken the sensitivity of the kinetic energy of $e_g$ electrons on the degree of lattice distortion in $La_{1-x}Ba_xMnO_3$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.204.1-204.1
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• 2013

Fluorine, the radius of which is close to that of oxygen, could be an appropriate anion doping candidate. A lower lattice distortion could be expected for F doping, compared with Al, Ga, and In doping. F-doped ZnO (FZO) and undoped ZnO nanorods were grown onto glass substrate by the hydrothemal method. The doping level in the solution, designated by F/Zn atomic ratio of was varied from 0.0 to 10.0 in 2.0 steps. To investigate the effects of the structure and optical properties of FZO nanorods were investigated using X-ray diffraction, UV-visible spectroscopy and photoluminescence (PL). For the PL spectra, the maximum peak position of NBE moves to higher energy, from 0 to 4 at.%. As the doping concentration increases, the maximum peak position of NBE gradually moves to lover energy, from 4 to 10 at.%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.648-651
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• 2004

Pb0.5Sr0.5TiO3(PST) thin films were deposited on the LaNiO3 (LNO(100))/Si and Pt/Ti/SiO2/Si substrates by the alkoxide-based sol-gel method. Structural and dielectric properties of PST thin films for the tunable microwave device applications were investigated. The PST films, which were directly grown on the Pt/Ti/SiO2/Si substrates showed the random orientation. For the LNO/Si substrates, the PST thin films exhibited highly (100) orientation. Compared with randomly oriented films, the highly (100)-oriented PST thin films showed better dielectric constant, tunability, and figure of merit (FOM). The dielectric constant, tunability, and FOM of the highly (100)-oriented PST thin film increased with increasing annealing temperature due to the decrease in lattice distortion. The differences in dielectric properties may be attributed to the change in the film stress and the in-plane oriented Polar axis depending on the substrate was used. The dielectric constants, dielectric loss and tunability of the PST thin films deposited on the LNO/Si substrates measured at 1 MHz were 483, 0.002, and 60.1%, respectively.

• Bulletin of the Korean Chemical Society
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• 제22권11호
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• pp.1231-1235
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• 2001

Pseudotetragonal ZrO0.75S whose space group is P212121 was synthesized and the cell dimensions were a=5.110(2) $\AA$, b=5.110(7) $\AA$, and c=5.198(8) $\AA.$ The space group P212121 seems to be resulted from lowering the symmetry of cubic ZrOS structure with P213 space group by lattice distortion due to the oxygen defects. In the distorted structure, bond shortening between metal-nonmetal by reduction of cell volume and alternation of Zr-Zr distance were observed. Dielectric constant and loss data of the bulk material in temperature range -170 to 20 $^{\circ}C$ and frequency range 50 Hz to 1 MHz showed that there was dielectric transition at around -70 $^{\circ}C$ originated from the relaxation of Zr-S segment. Comparing with ZrO2 exhibited the dielectirc constants, 9.0 at room temperature, ZrO0.75S showed high dielectric constant, k = 200.2 at 100 kHz. The activation energy of relaxation time due to dielectric relaxation of Zr-S was 0.47 eV (11.3 kcal/mole). According to the impedance spectra, ZrO0.75S showed more parallel circuit character between the resistance and capacitance components at the temperature (-70 $^{\circ}C)$ that the Zr-S dielectric relaxation was observed.

• 한국결정성장학회지
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• 제33권4호
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• pp.132-138
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• 2023

Doped and undoped-BiVO₄ samples with different elements (Li, Mg) and amounts were synthesized with a hydrothermal method. The synthesized samples were characterized using various techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusion reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity of the samples was evaluated by measuring the degradation of methyl blue (MB) under visible light irradiation. The results indicated that the incorporation of Mg and Li into BiVO₄ caused lattice distortion, the presence of surface hydroxyl groups, a narrower band gap, and a reduced recombination ratio of photo-induced electron-hole pairs. Notably, the photocatalytic activity of Mg5%-Li5% co-doped BiVO₄ sample exhibited a significant improvement compared to that of undoped BiVO₄ sample.