• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.278-282
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• 2010

The doping effect of thulium on electrical properties and degradation behavior in barium titanate ceramics ($BaTiO_3$) was investigated in terms of generations of core-shell structure and micro-chemical changes through highly accelerated degradation test. The dielectric specimens of pellet type and multi-layered sheets were prepared by using $BaTiO_3$ with undoped and doped with 1 mol% $Tm_2O_3$. The $BaTiO_3$ ceramics doped with 1 mol% $Tm_2O_3$ had 40% higher dielectric constant (${\varepsilon}$ = 2700) than that of the undoped $BaTiO_3$ specimen at curie temperature and met X7R specification. According to the result of highly accelerated degradation test conducted at $150^{\circ}C$, 70 V, and 24 hr, the oxygen diffusion was declined in dielectrics doped with 1 mol% $Tm_2O_3$. The $Tm^{3+}$ ion substituted selectively Ba site and Ti site and contributed to the generation of the core-shell structure. Oxygen vacancies occurred by substitution for Ti site could reduce excess oxygen that reacted to the Ni electrode.

• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.491-497
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• 1987

$ThO_2-Tm_2O_3$ (TDT) solid solutions containing 1,3,5,8,10, and 15 mol% $Tm_2O_3$ were synthesized from spectroscopically pure $ThO_2$ and $Tm_2O_3$ polycrystalline powders. The TDT solid solutions were indentified to the fluorite structure by the X-ray powder technique. The values of the lattice parameter were decreased with increasing amount of $Tm_2O_3$ incorporated. But, there was no linearity for the samples containing 8, 10, and 15 mol% $Tm_2O_3$. It was concluded that these samples became incomplete solid solutions. From the intensity analyses of X-ray diffraction patterns, the residual factor was found below 0.13 even for the 15 mol% TDT system. lt was confirmed from the DTA and TGA analyses that any phase transitions did not occur under the experimental condition executed. Comparing the pycnometric density with the lattice parameter obtained from XRD, it was suggested that the predominant defect model be an oxygen vacancy.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.25-29
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• 2010

Thulium oxide-doped barium titanate ceramics for MLCCs with perovskite structure were prepared by a sintering process at $1320^{\circ}C$ for 2 h in a reduced atmosphere. The effect of $Tm_2O_3$ addition on dielectric property of barium titanate ceramics has been studied in terms of their microstructures. Moreover, the phase identification of the dielectric specimens was conducted to define the secondary phase (pyrochlore). The specimen doped with 1 mol% $Tm_2O_3$ exhibited the highest dielectric constant. However, the dielectric constants of specimens with more than 2 mol% $Tm_2O_3$ to $BaTiO_3$ were the lower values than that of 1 mol% doped one. The grain size and the formation of pyrochlore phase associated with the dielectric properties were examined through morphology development and the structural analysis. Furthermore, these data were compared with the property of the dielectric material doped with $Er_2O_3$. It could be concluded that the dielectric property of ceramic capacitors were attributed to the change of pyrochlore phase and the tetragonality of $BaTiO_3$ with doping.

• Journal of the Korean Chemical Society
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• v.31 no.6
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• pp.498-502
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• 1987

Electrical conductivities of $(ZrO_2)_x-(Tm_2O_3)_y$ systems containing 1, 3 and 5mol% of $ZrO_2$ have been measured as a function of temperature and of oxygen partial pressure at temperatures from 600 to 1,100$^{\circ}$C and oxygen partial pressures from $10^{-5}$ to $2{\times}10^{-1}atm$. Plots of log conductivity vs. 1/T are found to be linear and average activation energy is 1.51 eV. The electrical conductivity dependences on PO$_2$ are different at two temperature regions, indicating ${\sigma}{\alpha}PO_2^{1/5.3}$ and ${\sigma}{\alpha}PO_2^{1/10.7}$ at high-and low-temperature regions, respectively. The defect of $(ZrO_2)_x-(Tm_2O_3)_y$ system is $V_{Tm}^{'''}$ and an electron hole is suggested as a carrier at high temperature region. At low temperature region, a mixed ionic and hole conduction is reasonable.

• Journal of the Korean Ceramic Society
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• v.38 no.2
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• pp.112-116
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• 2001

고상반응법에 의한 제조한 ZnGa$_2$O$_4$형광체에 Li 및 Tm 원소를 도핑함에 따른 발광특성을 조사하였다. 254nm 여기 하에서, 환원 처리된 ZnGa$_2$O$_4$형광체는 245nm에서 흡수피크와 380nm에서 발광피크를 나타내며, 이는 스피넬 구조에서 Ga$^{3+}$ 이온의 $^4$T$_2$$\longrightarrow$$^4$A$_2$천이에 기인한다. ZnGa$_2$O$_4$형광체에 있어서 Li 및 Tm을 도핑했을 경우가 도핑하지 않은 시료에 비해 발광강도 및 색순도가 개선되었으며, Li 및 Tm을 각각 0.1 mol, 0.01 mol 첨가했을 때 가장 우수한 발광강도 및 색순도 특성을 보였다.

• Korean Journal of Materials Research
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• v.28 no.6
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• pp.355-360
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• 2018

$LuNbO_4:0.2Yb^{3+},xTm^{3+}$ powders were prepared using a solid-state reaction process. The effects of the amount of Tm on up-conversion(UC) and down-conversion(DC) luminescence properties are investigated. X-ray diffraction patterns confirm that $Yb^{3+}$ and $Tm^{3+}$ ions are successfully incorporated into Lu sites. Under 980 nm excitation, the UC spectra of the powders predominantly exhibit strong near-infrared emission bands that peak at 805 nm, whereas weak 480 nm emission bands are observed as well. The emission bands are assigned to the $^1G_4{\rightarrow}^3H_6$ (480 nm) and 3 $^3H_4{\rightarrow}^3H_6$ (805 nm) transitions of the $Tm^{3+}$ ions via an energy transfer from $Yb^{3+}$ to $Tm^{3+}$; two- and three-photon UC processes are responsible for the 805 and 480 nm emissions, respectively. The DC emission spectra exhibit blue emission ($^1D_2{\rightarrow}^3F_4$) of $Tm^{3+}$ at 458 nm. The amount of Tm affects the emission intensity with the strongest emissions at x = 0.007 and 0.02 for the UC and DC luminescence, respectively. The results demonstrate that $LuNbO_4:Yb^{3+},Tm^{3+}$ phosphors are suitable for bio-applications.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.134-138
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• 1997

$Dy^{3+}-(or Tm^{3+}-)$ doped $Ga_2O_3 \;and\; ZnGa_2O_4$ phosphors were prepared using the solid state reaction method to investigate their photoluminescent characteristics. Under 254 nm excitation, $Dy^{3+}-doped Ga2_O_3$ exhibited two emission bands of 460~505nm and 570~600nm. On the other hand, $Dy^{3+}-(or Tm^{3+}-)$ doped $ZnGa_2O_4 $phosphors exhibited a broad-band emission extending from 330 nm to 610 nm, peaking at about 430 nm(or 370 nm). In this study, an emission peak shift of nealy 50 nm towards longer wavelength region was observed with $Dy^{3+}$ doping in the $ZnGa_2O_4 $.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.662-665
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• 2002

The microwave dielectric properties and the microstructures of $Tm_2O_3$-modified $BiNbO_4$ ceramics were investigated. $Bi_{(1-x)}Tm_xNbO_4$ ceramics combined with orthorhombic and triclinic phases were identified at sintering temperatures of $920{\sim}960^{\circ}C$. The apparent density decreased slightly with the increasing Tm content. Regardless of the Tm content the dielectric constant $(\varepsilon_r)$ of all compositions except x=0.1 in $Bi_{(1-x)}Tm_xNbO_4$ ceramics saturated at the range of 42~44. The $Q{\times}f_0$ values of 6,000-12,000(GHz) were obtained for all compositions when the sintering temperatures were in the range of $920{\sim}960^{\circ}C$. The temperature coefficient of the resonant frequency$(\tau_f)$ can be also adjusted with increasing the amount of the doped Tm from a positive value of $+15ppm/^{\circ}C$ to a negative value of $-20ppm/^{\circ}C$. The $Bi_{(1-x)}Tm_xNbO_4$ ceramics can be possibly applied to multilayer microwave devices with low processing temperatures.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2209-2213
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• 2009

$REBa_{2}Cu_{3}O_{7-d}$(REBCO) coated conductors(REBCO CCs) have been studied for electric power applications which require high current density wires. As long as the critical transition temperature(Tc) is concerned, REBCO CCs with large $RE^{3+}$ ions have been expected to have better current transport properties than those with smaller $RE^{3+}$ ions. For this reason, REBCO's with large $RE^{3+}$ ions which include GdBCO, NdBCO and SmBCO have been mainly considered as the superconducting layer of CCs. On the other hand, REBCO's with smaller $RE^{3+}$ions are expected to have advantages in the fabrication process of CCs because of the lower melting temperature. But it has not yet been made clear which REBCO is the most suitable for the superconducting layer of CCs. In this study, we investigated the current transport properties of REBCO CCs with small $RE^{3+}$ ion and advantages of using that in the CC fabrication process. Thin films of TmBCO, which has smaller $RE^{3+}$ion than most other $RE^{3+}$ ions, were fabricated on buffered metal substrate as the superconducting layer of CC by PLD process. TmBCO CC shows critical current density (Jc (77 K, sf) = $2.3\;MA/cm^2$) high enough to be utilized for application in electric power devices. Compared with previous experiments using the same PLD system, deposition temperature was approximately $20^{\circ}C$ lower than NdBCO thin films on buffered metal substrates.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.1-6
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• 2005

In this study we investigate the electronic structure and magnetism of transition metal (TM = Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag ) deped ZnO($TM_{0.25}Zn_{0.75}O$), which are expected to have Curie temperature. Full-potential Linearized Augmented Plane Wave(FLAPW) metod is adopted with exchange-correlation potential expressed as general gradient approximation(GGA). The calculated magnetic moments of ($TM_{0.25}Zn_{0.75}O$) are 0.83, 3.03, 4.03, 3.48, 2.47, 1.56, 0.43, 0.75, 0.01 ${\mu}_B$ for TM = Ti, Cr, Mn, Fe, Co, Ni, Ru, Pd, Ag, respectively. The nearest neighbor O atom to the transition metal is calculated to have a significant magnetic moment of about 0.1${\mu}_B$, ?? 새 strong hybridization between O-p and TM-d bands. As the results, the systems may have larger magnetic moments in total, compared to the corresponding isolated atoms. The 3d TM doped systems exhibit the half-metallic character except Co, wheres the 4d TM doped systems behave like normal metals and low spin polarization at the Fermi levels.