• 한국세라믹학회지
• /
• 제51권3호
• /
• pp.224-230
• /
• 2014

Nano-sized gadolinium-doped ceria (GDC)/nickel particle-dispersed $La_ySr_{1-y}Ti_{1-x}Fe_xO_3$ (LSFTO)-based composite solid oxide fuel cell anodes were fabricated by an infiltration method and the effects of the GDC/Ni nanoparticles on the anode polarization resistance and cell performance were investigated in terms of the infiltration time and nickel content. The anodic polarization resistance of the LSFTO anode was significantly enhanced by GDC and/or Ni infiltration and it decreased with increasing infiltration time and Ni content, respectively. It is believed that the observed phenomena are associated with enhancement of the ionic conductivity and catalytic activity in the nanocomposite anodes by the addition of GDC and Ni. Power densities of cells with the LSFTO and LSFTO-GDC/Ni nanocomposite anodes were 150 and $300mW/cm^2$ at $800^{\circ}C$, respectively.

• 한국전기전자재료학회논문지
• /
• 제14권11호
• /
• pp.879-884
• /
• 2001

In this paper, the structural and dielectric properties of (Sr$_{l-x}$Ca$_{x}$)TiO$_3$ (0$\leq$x$\leq$0.2) -based grain boundary layer ceramics were investigated by XRD, SEM and HP4194A. The ceramics were fabricated by the conventional mixed oxide method. The sintering temperature and time were 1420~152$0^{\circ}C$ and 4 hours, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca. The average grain size was increased with increase of sintering temperature. The relative density of all specimens was 96~98%. The 2nd Phase formed by the thermal diffusion of CuO from the surface leads to very excellent dielectric properties, that is, $\varepsilon$$_{r}$>50000, tan $\delta$<0.05, $\Delta$C<$\pm$10%. The appropriate Ca content was under 15 ㏖%.s under 15 ㏖%.%.

• 한국세라믹학회지
• /
• 제51권1호
• /
• pp.51-56
• /
• 2014

Mixed ionic and electronic conducting $K_2NiF_4$-type oxide, $Nd_{2-x}Sr_xNiO_{4+\delta}$ (x = 0, 0.4, 0.6) powders were synthesized by a solid-state reaction technique and solid oxide fuel cells consisting of a $Nd_{2-x}Sr_xNiO_{4+\delta}-GDC$ cathode, a Ni-YSZ anode and 8YSZ as an electrolyte were fabricated. The effect of strontium substitution for neodymium on the electrical and electrochemical properties was examined. The electrical conductivity increased with an increase in the Sr doping content, while it appears that the excess oxygen (${\delta}$) decreased. Sr doping into $Nd_2NiO_{4+\delta}$ resulted in an increase in the cathode polarization resistance and an decrease in the power density of the cell. These phenomena may be associated with the decreased amount of excess oxygen noted in the $Nd_{2-x}Sr_xNiO_{4+\delta}$ cathode.

• The Korean Journal of Ceramics
• /
• 제6권2호
• /
• pp.116-119
• /
• 2000

The a-axis and c-axis prefer oriented SBT thin films could be deposited on Pt(111)/Ti/$SiO_2$$650^{\circ}C$). The c-axis preferred orientation of SBT film can be obtained by Sr deficiency and high compressive stress. However, the a-axis-oriented grains can be formed under stoichiometric Sr content and nearly stress-free state.

• 한국재료학회지
• /
• 제11권11호
• /
• pp.997-1000
• /
• 2001

Conducting perovskite oxide, $(Ba,Sr)RuO_3(BSR)$, which has many advantages for $(Ba,Sr)TiO_3(BST)$ due to their similarity in crystal structure, lattice constant and chemical composition, was prepared on n-type Si (100) by liquid delivery metalorganic chemical vapor deposition(LDMOCVD). The deposition characteristics of BSR were controlled by gas-phase mass-transfer in the experiment. The BSR films deposited at 50$0^{\circ}C$ and oxygen flow rate of 100 sccm(standard cc/min) showed an average roughness of 22 $\AA$and resistivity of 810 $\mu$$\Omega$-cm. The roughness of BSR films with oxygen flow rate showed a close relationship with the resistivity of films. BSR (110) peak shifted toward lower Bragg angle with increase of x in the$(Ba_x,Sr_{1-x})TiO_3$. The resistivity of BSR films increased from 810 to 924 $\mu$$\Omega$-cm with increase of Ba content(x).

• 한국주조공학회지
• /
• 제29권1호
• /
• pp.27-32
• /
• 2009

The microstructure of Al-7Si-0.4Mg-1Fe alloy mainly consists of aluminum dendrites, Al-Si eutectics, and $Al_5FeSi$ needles. When Mn was added to the alloy, the substantial amount of $Al_5FeSi$ phase was changed into Al(Mn,Fe)Si, however the needle-like morphology was almost unchanged. Combined additions of Cr or Sr with Mn to the base alloy resulted in rod-like Al(Mn, Fe,Si)Si phase. The tensile properties of as-cast alloys were enhanced by the Mn addition, especially when it was added with Sr. The tensile properties after T6 heat treatment was a little improved with 0.7%Mn addition, but Cr or Sr additions with Mn didn't show any positive effect on the properties of heat-treated alloys.

• 한국주조공학회지
• /
• 제39권4호
• /
• pp.61-74
• /
• 2019

The effects of Sr and (Ti-B) additives on the impact and fatigue properties of recycled (35% scrap content) AC4A aluminum alloy are investigated here. The acicular morphology of the eutectic Si phase of as-cast specimens was converted to the fibrous one with Sr additives. The grain size of the α-solid solution decreased by the addition of (Ti-B) additives. The crack initiation energy (E_i) of the impact absorption energy decreased due to the incorporation of an oxide film and inclusions depending on the scrap used. The modification of the eutectic Si morphology by Sr additives is considered as the main factor of the increase of the average impact absorption energy (E_t). The addition of (Ti-B) additives contributed to an increase in the occurrence of crack deflections due to the refining of α-Al grains, resulting in improved fatigue properties.

• Bulletin of the Korean Chemical Society
• /
• 제28권8호
• /
• pp.1280-1284
• /
• 2007

A series of Ca1-xSrxS:Eu (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) phosphors were synthesized by solid-state reactions. The Ca1-xSrxS:Eu phosphors have a strong absorption at 455 nm, which corresponds to the emission wavelength of a blue LED. The emission peak of Ca1-xSrxS:Eu is blue shifted from 655 to 618 nm with increasing Sr content. The characteristics of Ca1-xSrxS:Eu phosphors make them suitable for use as wavelengthtunable red-emitting phosphors for three-band white LEDs pumped by a blue LED. In support of this, we fabricated a three-band white LED by coating SrGa2S4:Eu and Ca0.6Sr0.4S:Eu phosphors onto a blue LED chip, and characterized its optical properties.

• 한국전기전자재료학회논문지
• /
• 제15권1호
• /
• pp.24-29
• /
• 2002

In this paper, the microstructure and the dielectric properties of Sr$\_$1-x/CaxTiO$_3$(0$\leq$x$\leq$0.2)-based grain boundary layer ceramics were investigated. The sintering temperature and time were 1420∼152 0$\^{C}$ and 4 hours in N$_2$ gas, respectively. The average grain size and the lattice constant were decreased with increasing content of Ca, but the average grain size was increased with increase of sintering temperature. The second phase foamed by the thermal diffusion of CuO from the surface leads to verb high apparent dielectric constant, $\xi$$\_$r/>50000 and low dielectric loss, tan$\delta$<0.05. X-ray diffraction patterns of Sr$\_$1-x/CaxTiO$_3$ exhibited cubic structure, and the peaks shifted upward and the peak intensity were decreased with x. This is due to the lattice contraction as Sr is replaced by Ca with a smaller ionic radius. The specimens treated thermal diffusion for 2hrs in 1150$\^{C}$ exhibited nonlinear current-voltage characteristic, and its nonlinear coefficient(a) was overt 7.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
• /
• pp.2013-2015
• /
• 2005

In this paper, Effect of $BaSrTiO_3/Li_2CO_3$ on low temperature sintering and dielectric property of thick films has been investigated for variable capacitor on high frequency. The thick films were fabricated by the tape casting and then the structural and dielectric properties as a function of an addition composition ratio and sintering temperature were studied. For the thick film sintered at $1050^{\circ}C$, it was densified to 96% of $BaSrTiO_3$ theoretical density by the addition of 10 $wt{\cdot}%$ $BaSrTiO_3/Li_2CO_3$. Dielectric constant increased and Curie temperature lowered with the increased of $BaSrTiO_3/Li_2CO_3$ content, which probably can be explained by the substitution of $Ba^{3+},Li^{1+}$ on $RaTiO_3$ lattice. The tunability and dielectric loss of the $BaSrTiO_3/Li_2CO_3$ thick film, sintered at $1350^{\circ}C$, were about 26% and 0.234 at $10{\sim}15MHz$, respectively.