• 반도체디스플레이기술학회지
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• 제10권1호
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• pp.95-99
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• 2011

$(1-x)BaTiO_3+(x)Cd_5(PO_4)_3Cl$ ceramics were prepared by the conventional ceramic technique, i.e., solid state reaction at high temperature. The concentration of $Cd_5(PO_4)_3C$ was varied from 0.01 to 0.15 mole fraction. In order to study the phase transitions of our ceramics, the Raman scattering spectra were measured as functions of concentration x and temperature. It was found that the soluble limit of $Cd_5(PO_4)_3Cl$ in $BaTiO_3$ was the x=0.05 composition and $BaTiO_3$ phase disappeared above x=0.10. A new phase identified as $Ba_4Ti_3P_2O_{15}$ was detected in all samples of our compositions. The Curie temperature shifts up to $130^{\circ}C$ as the concentration x increases from zero to 0.05 and shift down to $95^{\circ}C$ as further increases to 0.08. For the increase of the Curie temperature, it is suggested that it can result from the inhibition of displacement of $Ti^{4+}$ in the distorted octahedron due to well dispersed $Ba_4Ti_3P_2O_{15}$ and $Cd_5(PO_4)_3Cl$ phase.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.93.1-93.1
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• 2000

• 한국재료학회지
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• 제18권4호
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• pp.222-227
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• 2008

In this study, $BaTiO_3$ thin films were grown by RF-magnetron sputtering, and the effects of a post-annealing process on the structural characteristics of the $BaTiO_3$ thin films were investigated. For the crystallization of the grown thin films, post-annealing was carried out in air at an annealing temperature that varied from $500-1000^{\circ}C$. XRD results showed that the highest crystal quality was obtained from the samples annealed at $600-700^{\circ}C$. From the SEM analysis, no crystal grains were observed after annealing at temperatures ranging from 500 to $600^{\circ}C$; and 80 nm grains were obtained at $700^{\circ}C$. The surface roughness of the $BaTiO_3$ thin films from AFM measurements and the crystal quality from Raman analysis also showed that the optimum annealing temperature was $700^{\circ}C$. XPS results demonstrated that the binding energy of each element of the thin-film-type $BaTiO_3$ in this study shifted with the annealing temperature. Additionally, a Ti-rich phenomenon was observed for samples annealed at $1000^{\circ}C$. Depth-profiling analysis through a GDS (glow discharge spectrometer) showed that a stoichiometric composition could be obtained when the annealing temperature was in the range of 500 to $700^{\circ}C$. All of the results obtained in this study clearly demonstrate that an annealing temperature of $700^{\circ}C$ results in optimal structural properties of $BaTiO_3$ thin films in terms of their crystal quality, surface roughness, and composition.

• Bulletin of the Korean Chemical Society
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• 제22권3호
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• pp.298-302
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• 2001

A site preference of niobium atom in Rb2-xLa2Ti3-xNbxO10 (0.0 $\leq$ x $\leq1.0)$ and RbLa2-xCaxTi2-xNb1+xO10 (0.0 $\leq$ x $\leq2.0)$, which are the solid-solutions between Rb2La2Ti3O10 and RbCa2Nb3O10, has been investigated by Raman spectroscopy. The Raman spectra of Rb2-xLa2Ti3-xNbxO10 (0.0 $\leq$ x $\leq1.0)$ gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa2-xCaxTi2-xNb1+xO10 (0.0 $\leq$ x $\leq2.0)$ showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed only when the linear Rb-O-Ti linkage can be replaced by much stronger terminal Nb-O bond with double bond character. From comparison with the Raman spectroscopic behavior of CsLa2-xA’xTi2-xNb1+xO10 (A’ = Ca and Ba; 0.0 $\leqx\leq2.0)$, it is also proposed that a local difference in arrangement of interlayer atoms causes a significantly different solid acidity and photocatalytic activity of the layered perovskite oxides, despite their crystallographically similar structures.

• 한국세라믹학회지
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• 제45권12호
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• pp.821-826
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• 2008

Nanocrystallized glasses with the composition of $(50-x)BaO-xTiO_2-50SiO_2$ (x=10, 15, 16.7 and 20) have been prepared by heat-treatment at $T_x$ (crystallization onset temperature) for 3 h, and their optical properties, photoluminescence (PL), XRD and Raman spectra have been examined. The absorption edges of the glasses were red-shifted and the absorption coefficient increased with an increase of $TiO_2$. The glass subjected to the heat-treatment showed a dense formation of ${Ba_2}{TiSi_2}{O_8}$ crystals. The XRD and Raman results show that the nanocrystallized glasses formed fresnoite phase up to $TiO_2$ concentrations of 15 mol%. Further-more, blue luminescence with a peak at the wavelength of around 470nm was observed in the nanocrystallized glass, demon strating the optical multifunctional nanocrystallized material such as non-linear optics and photo-luminescence. It is thought that the blue luminescence from the ${Ba_2}{TiSi_2}{O_8}$ nanocrystallized glass originated from the presence of $Ti^{4+}$ incorporated into the fresnoite-type structure.

• 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.