• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.389-393
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• 2000

High-quality $Er^{3+}$ doped Mg : $LiNbO_3$single crystal fibers were grown by a micro-pulling down ($\mu$-PD) method. Single crystal fibers were pulled down through the nozzle, at a pulling down rate of 0.5 mm/min and using a Pt crucible with a nozzle 1 mm in diameter in air atmosphere. Defects such as bubbles, cracks and inclusions were not detected in any of the grown crystals. The optical transmission of Er : Mg : $LiNbO_3$crystal was measured and the energy levels of $Er_2O_3$ ion could be calculated. The photoluminescence spectrum of crystal fibers showed an energy band emission with the strongest line corresponding to the $^4I_{3/2}{\to}^4I_{15/2}$transition. The concentration dependence of the entire wavelength region emission intensity upon excitation intensity measured emission intensity for the 3 mol% MgO doped fibers was larger than that for the 1, 5 mol% MgO doped fibers.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.491-495
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• 2005

(Zn,Mg)O (ZMO) thin films doped with Ga $(0\~0.03mol\%)$ in the target source were prepared by pulsed laser deposition on c-plane sapphire substrates at $500^{\circ}C$, and the effect of Ga contents on the properties of the electrical, optical and crystal properties of the deposited films was investigated. From X-ray diffraction patterns, ZMO film doped with $0.02 mol\%$ Ga showed crystal structure with c-axis preferred orientation, showing only the (0002) and (0004) diffraction peaks. In contrast, ZMO film doped with $Ga=0.03 mol\%$ showed a randomly oriented crystal structure. All the samples were highly transparent, showing the transmittance values of above $85\%$ in the visible region. For all the Ga doped ZMO films, the value of energy band gap was found to be about 3.5 eV, regardless of their Ga contents. From the Hall measurements, the resistivity and the carrier density for the ZMO film doped with $0.01 mol\%$ Ga were about $5\times10^{-4}\Omega-cm$ and $2\times10^{21}cm^{-3}$, respectively.

• Korean Journal of Materials Research
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• v.18 no.8
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• pp.450-453
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• 2008

Mg-doped and In-Mg co-doped p-type GaN epilayers were grown in a low-pressure metal organic chemical vapor deposition technique. The effect of In doping on the p-GaN layer was studied through photoluminescence (PL), persistent photoconductivity (PPC), and transmission electron microscopy (TEM) at room temperature. For the In-doped p-GaN layer, the PL intensity increases significantly and the peak position shifts to 3.2 eV from 2.95 eV of conventional p-GaN. Additionally, In doping greatly reduces the PPC, which was very strong in conventional p-GaN. A reduction in the dislocation density is also evidenced upon In doping in p-GaN according to TEM images. The improved optical properties of the In-doped p-GaN layer are attributed to the high crystalline quality and to the active participation of incorporated Mg atoms.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.5
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• pp.447-453
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• 1999

Congruent $LiNbO_3$ crystals with doped Mg and codoped with Mn or Fe were grown by the Czochralski method. It is known that the physical properties of $LiNbO_3$ depend strongly on the addition of Mg and transition metals. This is established by studying the following properties; XRD patterns, the phase transition temperature, energy of the fundamental absorption edge, the shape of the absorption band of the $OH^-$ vibration and lines of the ESR of $Fe^{3+},\; Mn^{2+}$. The position of the UV absorption edge and the shape and peak point of the absorption band of the $OH^-$ vibrational band changed monotonously up to a critical concentration of $Mg^{2+}$ ions. The mechanism of the incorporation of Mg ions changes at this concentration. The transition temperature was estimated by measuring the dielectric temperature behavior up to $1230^{\circ}C$ in a frequency range of 100Hz to 10MHz. EPR of $Mn^{2+}\;and\; Fe^{3+}$ ions were employed to investigated the Mg doping effects in the $LiNbO_3$ crystal. The increase of linewidths and the asymmetry of signals were observed in all crystals. New signals of $Fe^{3+}$ arising from the new centers were observed I the heavily Mg-doped crystals.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.139-143
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• 1997

The doping effects of Mg and/or Fe ions on congruent LiNbO$_3$ single crystal growth were studied in order to clarify the roles of MgO in Fe doped LiNbO$_3$ single crystals. The effective distribution coefficienct of Fe was found decreased drastically from 0.85 to 0.5 by the addition of MgO into the LiNbO$_3$ melt. M ssbauer spectra revealed that the addition of MgO reduces the occurrence of Fe2+ ions during growth in air. Therefore, it is likely that there would be two important roles of MgO in Fe doped LiNbO$_3$. One is to suppress the incorporation of all Fe ions, and the other is to reduce the concentration of Fe2+ ions among the total Fe ions.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.377-380
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• 2008

In this work, we measured the spatiotemporal surface charge distribution by the longitudinal electro-optic amplitude modulation method with BSO single crystal to investigate the decay and diffusion characteristics of surface charges in three types of MgO. The speed of decay and diffusion of two different kinds doped MgO is compared with those of pure MgO. The difference in the characteristics of the decay and diffusion between the electron and ion surface charges is investigated separately. We found that the rate of ion decay is the major factor that makes the difference of the temporal variation of wall voltage among different types doped MgO.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1029-1038
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• 1993

The microstructures of aluminas, included of dissolved CaO as $\alpha$-alumina seeded pseudo-boehmite hydrosol was gelled in plaster mold and doped of MgO as dipping of calcines(120$0^{\circ}C$-2h) into Mg-nitrate solution, were compared to the one of which additives are excluded during the gellation. It was formed the boundary layer of 300~350${\mu}{\textrm}{m}$ distance from surface to the inside, containing of approximately 500ppm CaO by dissolved Ca from plaster mold. As the MgO addition to the boundary layer with dissolved CaO, the microstructure of the layer was uniformed and inhibited the grian growth, compared to one of that additives be excluded specimen and of MgO doped-inside region. This result was considered as abnormal grain growth and effect of flat boundary formation be appeared by effects of dissolved CaO, were decreased by MgO co-doping.

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.147-151
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• 2007

An improvement for the efficiency of the $Sr_{2}SiO_{4}:Eu$ yellow phosphor under the $450{\sim}470\;nm$ excitation range have been achieved by adding the co-doping element ($Mg^{2+}\;and\;Ba^{2+}$) in the host. White LEDs were fabricated through an integration of an blue (InGaN) chip (${\lambda}_{cm}=450\;nm$) and a blend of two phosphors ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) in a single package. The InGaN-based two phosphor blends ($Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor) LEDs showed three bands at 450 nm, 550 nm and 640 nm, respectively. The 450 nm emission band was due to a radiative recombination from an InGaN active layer. This 450 nm emission was used as an optical transition of the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor. As a consequence of a preparation of white LEDs using the $Mg^{2+},\;Ba^{2+}\;co-doped\;Sr_{2}SiO_{4}:Eu$ yellow phosphor+CaS:Eu red phosphor yellow phosphor and CaS:Eu red phosphor, the highest luminescence efficiency was obtained at the 0.03 mol $Ba^{2+}$ concentration. At this time, the white LEDs showed the CCT (5300 K), CRI (89.9) and luminous efficacy (17.34 lm/W).

• Carbon letters
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• v.11 no.4
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• pp.332-335
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• 2010

The photodegradation of the model compounds Quinol, an aromatic organic compound and Acid blue FFS, an acid dye of chemical class Triphenylmethane was studied by using illumination with UV lamp of light intensity 250W. $TiO_2$ and $TiO_2$ doped with Boron and Nitrogen was used as catalyst. The sol-gel method was followed with titanium isopropoxide as precursor and doping was done using Boron and Nitrogen. In photocatalytic degradation, $TiO_2$ and doped $TiO_2$ dosage, UV illumination time and initial concentration of the compounds were changed and examined in order to determine the optimal experimental conditions. Operational time was optimized for 360 min. The optimum dosage of $TiO_2$ and BN doped $TiO_2$ was obtained to be 2 $mgL^{-1}$ and 2.5 $mgL^{-1}$ respectively. Maximum degradation % for quinol and Blue FFS acid dye was 78 and 95 respectively, at the optimum dosage of BN-doped $TiO_2$ catalyst. It was 10 and 4% higher than when undoped $TiO_2$ catalyst was used.

• Journal of Electrochemical Science and Technology
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• v.4 no.3
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• pp.102-107
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• 2013

The electrochemical properties of Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ and pure $LiFe_{0.5}Mn_{0.5}PO_4$ olivine cathodes are examined and the lattice parameters are refined by Rietveld analysis. The calculated atomic parameters from the refinement show that $Mg^{2+}$ doping has a significant effect in the olivine $LiFeMnPO_4$ structure. The unit cell volume is 297.053(2) ${\AA}^3$ for pure $LiFe_{0.5}Mn_{0.5}PO_4$ and is decreased to 296.177(1) ${\AA}^3$ for Mg-doped $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample. The doping of $Mg^{2+}$ cation with atomic radius smaller than $Mn^{2+}$ and $Fe^{2+}$ ion induces longer Li-O bond length in $LiO_6$ octahedra of the olivine structure. The larger interstitial sites in $LiO_6$ octahedra facilitate the lithium ion migration and also enhance the diffusion kinetics of olivine cathode material. The $LiFe_{0.48}Mn_{0.48}Mg_{0.04}PO_4$ sample with larger Li-O bond length delivers higher discharge capacities and also notably increases the rate capability of the electrode.