• Korean Journal of Materials Research
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• v.20 no.5
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• pp.257-261
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• 2010

A non-volatile resistive random access memory (RRAM) device with a Cr-doped $SrZrO_3/SrRuO_3$ bottom electrode heterostructure was fabricated on $SrTiO_3$ substrates using pulsed laser deposition. During the deposition process, the substrate temperature was $650^{\circ}C$ and the variable ambient oxygen pressure had a range of 50-250 mTorr. The sensitive dependences of the film structure on the processing oxygen pressure are important in controlling the bistable resistive switching of the Cr-doped $SrZrO_3$ film. Therefore, oxygen pressure plays a crucial role in determining electrical properties and film growth characteristics such as various microstructural defects and crystallization. Inside, the microstructure and crystallinity of the Cr-doped $SrZrO_3$ film by oxygen pressure were strong effects on the set, reset switching voltage of the Cr-doped $SrZrO_3$. The bistable switching is related to the defects and controls their number and structure. Therefore, the relation of defects generated and resistive switching behavior by oxygen pressure change will be discussed. We found that deposition conditions and ambient oxygen pressure highly affect the switching behavior. It is suggested that the interface between the top electrode and Cr-doped $SrZrO_3$ perovskite plays an important role in the resistive switching behavior. From I-V characteristics, a typical ON state resistance of $100-200\;{\Omega}$ and a typical OFF state resistance of $1-2\;k{\Omega}$, were observed. These transition metal-doped perovskite thin films can be used for memory device applications due to their high ON/OFF ratio, simple device structure, and non-volatility.

• Korean Journal of Materials Research
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• v.20 no.5
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• pp.241-245
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• 2010

One of the weak points of the Cr-doped SZO is that until now, it has only been fabricated on perovskite substrates, whereas NiO-ReRAM devices have already been deposited on Si substrates. The fabrication of RAM devices on Si substrates is important for commercialization because conventional electronics are based mainly on silicon materials. Cr-doped ReRAM will find a wide range of applications in embedded systems or conventional memory device manufacturing processes if it can be fabricated on Si substrates. For application of the commercial memory device, Cr-doped $SrZrO_3$ perovskite thin films were deposited on a $SrRuO_3$ bottom electrode/Si(100)substrate using pulsed laser deposition. XRD peaks corresponding to the (112), (004) and (132) planes of both the SZO and SRO were observed with the highest intensity along the (112) direction. The positions of the SZO grains matched those of the SRO grains. A well-controlled interface between the $SrZrO_3$:Cr perovskite and the $SrRuO_3$ bottom electrode were fabricated, so that good resistive switching behavior was observed with an on/off ratio higher than $10^2$. A pulse test showed the switching behavior of the Pt/$SrZrO_3:Cr/SrRuO^3$ device under a pulse of 10 kHz for $10^4$ cycles. The resistive switching memory devices made of the Cr-doped $SrZrO_3$ thin films deposited on Si substrates are expected to be more compatible with conventional Si-based electronics.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.30.1-30.1
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• 2007

• Journal of Magnetics
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• v.8 no.4
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• pp.142-145
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• 2003

Valence states and electronic structures of Cr-doped $Nd_{1/2}A_{1/2}Mn_{1-y}Cr_{y}O_3$(NAMO; A=Ca, Sr) manganites have been investigated using x-ray absorption spectroscopy (XAS) and high-resolution photoemission spectroscopy (PES). All the Cr-doped NAMO systems exhibit the clear metallic Fermi edges in the Mn $e_{g}$ PES spectra near $E_{F}$. The spectral intensity at $E_{F}$ is higher for Cr-doped N $d_{l}$ 2/S $r_{l}$ 2/Mn $O_3$(NSMO) than for Cr-doped N $d_{l}$ 2/C $a_{l}$ 2/Mn $O_3$ (NCMO), reflecting the stronger metallic nature for NSMO than for NCMO. The measured Cr 2p XAS spectra are found to be very similar to that of C $r_2$ $O_3$, indicating that Cr ions in Cr-doped NAMO are in the trivalent C states ( $t^3$$_{2g}$). The Cr 2p XAS data are consistent with the Cr 3d PES spectra located at ∼1.3 eV below $E_{F}$ and having no emission near $E_{F}$.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.450-456
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• 2010

During the process of synthesizing green celsian pigments, attempts were made to replace a given amount of $BaCO_3$ with $SrCO_3$ to accelerate the hexagonal to monoclinic celsian phase transition, which was assumed to promote color development. Monoclinic celsian have been synthesized from Hongkong-Kaolin, $BaCO_3$, $SrCO_3$, $Al(OH)_3$, $SiO_2$ and $SrCO_3$ with 1 to 1.5 wt% of LiF as a mineralizer from 1100 to $1300^{\circ}C$. It was found that replacing $BaCO_3$ with $SrCO_3$ allowed monoclinic celsian to be formed at a lower temperature. While the pigments containing 1 mole of $BaCO_3$ were difficult to synthesize monoclinic celsian with absence of the mineralizer, the formation of monoclinic celsian was successfully achieved even without mineralizer by using 0.25 mole of $SrCO_3$ at $1250^{\circ}C$ for 1 h. The color development was improved from yellowish green to green with increasing amount of $SrCO_3$ being replaced.

• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.162-167
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• 2005

Using Pechini method, we synthesized the $La_{0.6}Ca_{0.41}CrO_3$ (LCC41) and $La_{0.8}Sr_{0.05}Ca_{0.15}CrO_3$ (LSCC) powders for slurry dip coating, and $La_{0.75}Ca_{0.27}CrO_3$ (LCC27) powder for air plasma spray coating. The sintering property of the powders and their coating properties were investigated. The average particle sizes of the LCC41, LSCC, LCC27 were 0.6, 0.9, $1.5{\mu}m$, respectively. The relative density of LCC41 bulk was to be found about 98%. The LSCC coating on anode support prevented Ca migration of the coated LCC41 on the anode some or less, which was confirmed from EDS result. The air plasma spray-coated LCC27 with the dip-coated LCC41 were more dense and showed better electrical conductivity than those of the air plasma spray-coated LCC27 and the dip-coated LSCC and LSCC41. The LCC41 and LCC27 showed good electrical conductivities, but the LSCC had a poor electrical conductivity probably due to low sinterability

• Bulletin of the Korean Chemical Society
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• v.23 no.10
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• pp.1463-1482
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• 2002

Partially doped Aurivillius phases SrBi2N$b_{2-x}M_xO_9$ (M=Cr and Mo) were successfully synthesized and characterized. The extent of the substitution was limited at ~20 mole % because of the size differences between $Nb^{5+}$ and $Cr^{6+}$, and between $Nb^{5+}$ and $Mo^{6+}$. When the amount of substitution exceeded ~20 mole%, the phases began to collapse and the second phases were made. The dielectric constants of substituted compounds were enlarged nevertheless Cr or Mo is substituted. The increment is bigger in the Mo substituted compound than in the Cr doped one although the Nb(Cr)$O_6$ octahedra could be more strongly distorted than the Nb(Mo)$O_6$ octahedra since the ionic size difference between $Nb^{5+}$ and of $Cr^{6+}$ is much bigger than that between $Nb^{5+}$ and $Mo^{6+}$. Consequently, the dielectric constant of the substituted Aurivillius phase $Bi_2$A_{n-1}B_{n-x}M_xO_{3n+1}$$ depends on the extent of distortion of the B$O_6$ octahedra and more strongly on the polarizability of the metal.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1135-1141
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• 2008

The $La_{1-x}(Ca\;or\;Sr)xCrO_3$(x=0 and 0.25) interconnect materials for high temperature electrolysis of steam were investigated in views of sinterability and electrical conductivity. $LaCrO_3$, $La_{0.75}Ca_{0.25}CrO_3$ (LCC), and $La_{0.75}Sr_{0.25}CrO_3$ (LSC) powders were synthesized by coprecipitation method. Crystal structure was confirmed by X-ray diffraction (XRD). The sintering characteristics were analyzed by relative density and scanning electron microscopy. The electrical conductivity was measured by a DC four probe method. From the analyses of relative densities, it was found that the doped $LaCrO_3$ showed better sinterability than $LaCrO_3$ and the those sinterability increased with decrease of those particle sizes. The XRD results at different sintering temperatures for LCC and LSC revealed that the sinterability is closely related to the second phase transformation, that is, the second phase melting above $1,300^{\circ}C$ for LCC and $1,400^{\circ}C$ for LSC significantly promotes the sinterability. In case of electrical conductivities of LCC and LSC, which had a similar relative density, LCC showed better electrical conductivity than LSC.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.715-719
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• 2007

STS444 with or without $La_{0.9}Sr_{0.1}MnO_3$ (LSM)-coating was contacted to $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ (LSCF) cathode on various electrolyte materials and the polarization resistance $(R_p)$ was measured by impedance spectroscopy. By making a symmetric half-cell and contacting only one side of the cathode with the interconnect, the effect of chromium (Cr) poisoning was separated from the aging effects. When the LSCF cathode was contacted with LSM-coated STS (stainless steel), $R_p$ of LSCF was lower than that contacted with the uncoated STS. Impedance patterns measured for the working electrode (W.E.), the counter electrode (C.E.) at $600^{\circ}C$ in air were analyzed. Normalized data of net Cr effect showed that $Ce_{0.9}Gd_{0.1}O_2$ (GDC) electrolyte is more tolerant to the chromium poisoning than $La_{0.9}Sr_{0.1}Ga_{0.8}Mg_{0.2}$ (LSGM) or 8 mol% $Y_2O_3-doped$ $ZrO_2$ (YSZ) electrolytes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.44-50
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• 2018

The improved high-performance Fe-based perovskite-type oxides ($La_{0.7}Sr_{0.3}M_xFe_{1-x}O_3$, M = Cu, Cr, Ni) were synthesized by a citrate method and characterized by SEM, EDS, XRD and NMR spectroscopy analyses. The characterization analyses revealed that the stoichiometric amounts of lattice oxygen were existed in all of perovskite samples except for a nickel-doped perovskite. Fe-based perovskites exhibited a surprising result for ortho-para $H_2$ spin conversion reaction, indicating two orders of magnitude higher conversions and conversion rates than commercial $Fe_2O_3$. It was considered that this conversion difference might be attributed to the presence of oxygen vacancies in Fe-based perovskites prepared in this study.