• Journal of Magnetics
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• 제20권2호
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• pp.97-102
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• 2015

The waste of sintered Nd-Fe-B magnets was recycled using the method of dopingPrNd nanoparticles. The effect of PrNd nanoparticle doping on the magnetic properties of the regenerated magnets has been studied. As the content of the PrNd nanoparticles increases, the coercivity increases monotonically, whereas both the remanence and the maximum energy products reach the maximum values for 4 wt% PrNd doping. Microstructural observation reveals that the appropriate addition of PrNd nanoparticles improves the magnetic properties and refines the grain. Domain investigation shows that the self-pinning effect of the rare earth (Re)-rich phase is enhanced by PrNd nano-particle doping. Compared to the magnet with 4 wt% PrNd alloy prepared using the dual-alloy method, the regenerated magnet doped with the same number of PrNd nanoparticles exhibits better magnetic properties and a more homogeneous microstructure. Therefore, it is concluded that PrNd nanoparticle doping is an efficient method for recycling the leftover scraps of Nd-Fe-B magnets.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.5-8
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• 2015

The effects of Pr substitution on the structural and the superconducting properties for Pb-based 1201 cuprates with compositions of $(Pb_{0.5-x}Pr_xCd_{0.5})SrLaCuO_z(0{\leq}x{\leq}0.25)$ and $(Pb_{0.45}Pr_{0.05}Cd_{0.5})(Sr_{1-y}La_{1+y})CuO_z(0{\leq}y{\leq}0.1)$ were investigated. It is found that $T_c$ decreases as the Pr-doping content x increases in the $(Pb_{0.5-x}Pr_xCd_{0.5})SrLaCuO_z$ samples, whereas $T_c$ of $(Pb_{0.45}Pr_{0.05}Cd_{0.5})(Sr_{1-y}La_{1+y})CuO_z$ samples increases as the La-doping content y increases. The experimental results were discussed in connection with the change in hole concentration of the samples.

• Transactions on Electrical and Electronic Materials
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• 제8권6호
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• pp.234-240
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• 2007

The electrical properties and dc aging behavior for specified stress state of system, which is composed of quaternary Zn-Pr-Co-Cr, were investigated for different $Dy_2O_3$ addition doping level. As $Dy_2O_3$ doping level increased, the density decreased in the range of 5.51-4.90 $g/cm^3$, reaching maximum at 0.5 mol% and the average ZnO grain size decreased in the range of 17.7-6.0 ${\mu}m$. The incorporation of $Dy_2O_3$ significantly improved the non-ohmic properties, above 30 in non-ohmic coefficient, compared with that of undoped samples. The samples with the best performance of non-ohmic properties were obtained for $Dy_2O_3$ doping level of 1.0 mol%, with 49 in non-ohmic coefficient and 2.6 ${\mu}A/cm^2$ in leakage current. The samples with the highest stability were obtained for $Dy_2O_3$ doping level of 0.5 mol%.

• 한국전기전자재료학회논문지
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• 제19권10호
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• pp.971-975
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• 2006

[ $SrTiO_3:Al,Pr$ ] red phosphors doped with Y and Er were synthesized by solid state reaction method. The luminescence properties of $SrTiO_3:Al,Pr$ phosphors before and after doping were examined by photoluminescence. Efforts were paid to elucidate the cause of the increase of green luminescence in $(Sr_{0.95}Y_{0.05})TiO_3:Pr,Er\;and\;(Sr_{0.95}Y_{0.05})TiO_3:Pr,Al$ phosphors. The enhanced green luminescence was interpreted by the energy transfer between $Er^{3+}\;and\;Pr^{3+}$ ions, and the change of bandgap in the $(Sr_{0.95}Y_{0.05})TiO_3:Pr$ phosphors.

• 공업화학
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• 제7권6호
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• pp.1125-1131
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• 1996

고체전해질형 연료전지의 산소극 재료로서 페롭스카이트 구조를 갖는 $PrMnO_3$에 Ca과 Sr을 도핑시켜 도핑량에 따른 전기전도도, 산소환원과전압 등의 전기화학적 특성과, 전해질인 yttria stabilized zirconia와의 반응성 그리고 열 팽창률 등을 살펴 보았다. 합성된 페롭스카이트 분말은 대략 $2{\sim}5{\mu}m$의 평균입자 크기를 나타내었는데 이때 입자크기 및 비표면적은 도핑량과 무관하였다. Ca이 30mo1% 도핑되었을 때 전기전도도는 $1000^{\circ}C$에서 $266S{\cdot}cm^{-1}$로 가장 높은 값을 나타내었고, 분극을 통해 살펴 본 산소환원특성도 Ca이 30mol% 도핑되었을 때 가장 우수한 특성을 나타내었다. 전극물질과 전해질인 YSZ를 $1200^{\circ}C$에서 100시간 동안 반응시킨 결과 $PrMnO_3$에 Sr을 도핑시켰을 때보다 Ca을 도핑시킨 것이 반응성이 훨씬 약한 결과를 나타내었다. $Pr_{0.7}Ca_{0.3}MnO_3$의 열팽창계수는 $300{\sim}1000^{\circ}C$의 영역에서 $1.19{\times}10^{-5}K^{-1}$로 측정되었고 이 값은 YSZ의 열팽창계수 $1.15{\times}10^{-5}K^{-1}$과 유사한 값이었다.

• 한국전기전자재료학회논문지
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• 제13권7호
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• pp.551-556
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• 2000

We have investigated the effect of surface In composition with Si cell temperature on the In$_{0.1}$/Ga$_{0.9}$/As epilayers grown on GaAs substrates. The epilayers were grown by molecular beam epitaxy(MBE) method and were characterized by the pthotoreflectance(PR) measurements. The E$_{o}$ bandgap energies of In$_{0.1}$/Ga$_{0.9}$/As epilayers were observed at around 1.28 eV at room temperature, and the additional shoulder peaks appeared at the higher energies than E$_{o}$ with increase of Si doping concentrations. The intensity of the additional shoulder peak was decreased with lowering the measurement temperature and the peak disappeared with the increase of surface etching time. This results hows that In composition at surface of InGaAs epilayer is decreased with the increase of the doping cell temperature. We consider that the reason of the decrease of In composition at the surface should be due to In re-evaporation from the surface by radiation heat of Si doping cell.ell.ell.ell.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2512-2518
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• 2014

The praseodymium-doped $TiO_2$ photocatalyst samples, which could degrade methyl orange under UV irradiation, were prepared by sol-microwave method for improving the photocatalytic activity of $TiO_2$. The resulting materials were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectra, Fourier transform infrared spectra (FTIR) and Ultraviolet-visible diffuse reflectance spectra (UV-vis DRS). It was found Pr doping retarded the growth of crystalline size and the phase transformation from anatase to rutile, and narrowed the band gap energy. Praseodymium doping brought about remarkable improvement in the photoactivity. The optimal dopant amount of Pr was 2% by molar of cement and the calcination temperature was $500^{\circ}C$ for the best photocatalytic activity. The improvement of photocatalytic activity was ascribed to the occurrence of lattice distortion and the effective containment of the recombination of the electron-hole by $Pr^{3+}$.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.156.2-156.2
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• 2008

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.256-259
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• 1999

새로운 구리산화물 (Pb$_{0.5}$V$_{0.5}$)Sr$_2$(Ca$_{1-x}$Pr$_x$)Cu$_2$O$_z$를 상압의 산소 분위기 열처리를 통해 합성하였다. X선 회절실험결과 x=0.5 이상일 때 Pb-1212의 단일상이 형성됨을 확인했으며, 비저항 측정결과 x=0.5 인 시편에서 T$_c$(zero)=29 K T$_c$(onset)=40 K 가 관측되었다. x=0.6 이상일 때는 초전도 특성이 관측되지 않았으며 이는 Pr의 도핑량 x 가증가할수록 a 축이 증가하고 c 축이 감소 하는 것과 밀접히 연관되는 것으로 논의되었다.

• Progress in Superconductivity
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• 제13권3호
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• pp.158-162
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• 2012

$Y(Pr)Ba_2Cu_4O_8$ system is one of the most studied high temperature superconductors. Substitution of Pr for Y in this system suppresses $T_c$ and superconductivity finally disappears at a high Pr doping. There are competing theories for the suppression of $T_c$ but systematic experimental results are very rare. In order to find the change in Fermi surface topology which can affect the superconductivity, we have performed angle-resolved photoemission studies on single crystal samples of $YBa_2Cu_4O_8$ and $PrBa_2Cu_4O_8$. While the Fermi surface of $YBa_2Cu_4O_8$ shows a similar topology to those of other cuprates, we observe only 1D like band structures in $PrBa_2Cu_4O_8$. We find no significant differences in the chain band for both samples.