• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.507-512
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• 2001

The hydrothermal reaction between lanthanum(Ⅲ) nitrate $(La(NO3)3${\cdot}$6H_2O)$ and benzene-1,3-dicarboxylic acid $(H_2BDC)$ in the presence of 1,2-bis(4-pyridyl)ethane gave a 2-D lanthnum-BDC coordination polymer with an empirical formula of $〔La_4$(BDC)_6(H_2O)_5$〕(H_2O)$ (1). X-ray structure analysis of compound 1 revealed that this polymer contains four distinct La metals. The three La metals are 7-coordinate with three different structures: a capped trigonal prism, a capped octahedron, and a pentagonal bipyramid. The remaining La metal has a 8-coordinate, square antiprismatic structure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.42-48
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• 1998

Synthesis of PLT($Pb_{1-X}La_{2X/3}TiO_3$, x=0.1~0.3) powders was carried out by hydrothermal method. Optimal conditions for synthesis were $250^{\circ}C$ of reaction temperature, 8M-KOH solution of hydrothermal solvent and 12 hrs reaction time, and the monolithic $Pb_{1-X}La_{2X/3}TiO_3$ particles were obtained with the composition of x$\leq$0.2. The tetragonality(c/a) and the phase transition temperature were decreased by the increment of the $La_2O_3$ contents in PLT solid solutions, and the Curie temperature of the $Pb_{1-X}La_{2X/3}TiO_3$(x=0.2) was $400^{\circ}C$. The shape of the synthesized particles were nearly spherical and the size was in the 20~200 nm range.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.25-29
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• 1999

We have developed a laser molecular beam epitaxy system for the layer-by-layer growth of oxide thin films. Using this system, we could grow and control oxide thin films of LaAlO$_3$in a molecular layer epitaxy mode on the atomically flat SrTiO$_3$ substrate with a LaAlO$_3$single crystal target. Very clear RHEED oscillations were observed during to growth of a LaAlO$_3$ film for a long period under the optimized conditions of substrate temperature at $650^{\circ}C$, oxygen pressure at 1$\times$10\ulcorner torr, and an incident laser fluence of 4.6J/$\textrm{cm}^2$. The height of mono-layer-LaAlO$_3$ film grown during one period of RHEED intensity oscillation was 3.8$\AA$.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.387-392
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• 2007

Thermal conductivities in $La_2Ce_2O_7-Gd_2Ce_2O_7-Y_2Ce_2O_7$ ternary system have been investigated. Pyrochlore phases formed at all ternary compositions and their sinterbilities were decreased with La addition. Thermal conductivities showed a minimum value at $La_2Ce_2O_7$ with moderate increases as $Y^{3+}$ and $Gd^{3+}$ ions replaced $La^{3+}$. Thermal expansion anomaly observed in $La_2Ce_2O_7$, which might be detrimental to TBC application, were suppressed by $Y^{3+}$ and $Gd^{3+}$ additions, with resultant thermal conductivities, $1.3{\sim}1.5 W/mK$ at $1000^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.567-572
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• 1998

The crystalline structure of $LaTi_{0.8}V_{0.2}O_3$ solid solutions, prepared by arc-melting palletized mixtures of predried $La_2O_3,\;V_2O_3,\;TiO_2$, and Ti, was investigated by transmission electron microscopy and computer image simulation. Computer image simulations were performed by the multislice method for a wide range of sample thickness and defocusing value. The structure of $LaTi_{0.8}V_{0.2}O_3$ was determined as a $GdFeO_3$-type orthorhombic $(a\approx5.58{\AA},\;b\approx7.89{\AA},\;and\;c\approx5.58{\AA})$ with a space group $P_{nma-}$. No evidence of ordering of Ti and V atoms in $SaTi_{0.8}V_{0.2}O_3$ was found.

• Journal of the Korean Ceramic Society
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• v.34 no.11
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• pp.1129-1138
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• 1997

Al2O3/20 vol%YAG composite containing equiaxed grains and Al2O3/20 vol%LaAl11O18 composite containing elongated grains were fabricated using Al2O3-Y2O3 composition and Al2O3-La2O3 composition, respectively, by hot-pressing. In order to investigate the influence of microstructural control of second phase on toughening effect of toughened ceramic composites, AE (acoustic emission) measurements have been coupled with fracture toughness experiments(SENB and SEPB method). A separation of the fracture toughness and analysis of toughening mechanism was possible using the AE technique. The fracture toughness of hot-pressed materials was estimated to be 3.2 MPam0.5 for monolithic alumina, 4.7 MPam0.5 for Al2O3/20 vol%YAG composite and 6.2 MPam0.5 for Al2O3/20 vol%LaAl11O18 composite. In monolithic Al2O3, toughening does not occur as a result of either microcracking or grain bridging, whereas, composites exhibit toughening effects by both microcracking in the frontal zone and gain bridging in the wake zone, resulting in an improvement of fracture toughness as compared with monolithic Al2O3. The fracture toughness of Al2O3/20 vol%LaAl11O18 composite is higher than that of Al2O3/20 vol%YAG composite. It may be attributed to the elongated microstructure of Al2O3/20 vol%LaAl11O18 composite, resulting relatively greater bridging effect.

• Journal of Sensor Science and Technology
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• v.13 no.4
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• pp.298-302
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• 2004

Thick films of $LaNiO_{3}$ having perovskite structure impregnated with indium and bismuth oxides have been used as sensing material for acetonitrile ($CH_{3}CN$) gas. The sensor response for $CH_{3}CN$ is quite good with an excellent recovery for partial pressure from 3 ppm to 20 ppm between 200 and $250^{\circ}C$. $LaNiO_{3}$ alone has exhibited low response, but after impregnation of $In_{2}O_{3}$ and $Bi_{2}O_{3}$ have given increased sensitivity even with 3 ppm partial pressure of $CH_{3}CN$ at $200^{\circ}C$. It is assumed that $CH_{3}CN$ is undergoing oxidation reaction on surface of the film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.39-45
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• 2004

Fine LaAlO$_3$ powders wore successfully synthesized from La$_2$O$_3$ and ${\gamma}$ $Al_2$O$_3$ powders milling for 10∼50 hours via the high energy milling technique (mechanochemical method) in room temperature and air. The particle size of LaAlO$_3$ powder were estimated from XRD patterns and SEM images to be 160∼180 nm. The LaAlO$_3$ ceramics arc derived for the synthesized powders (milling for 10, 30 and 50 hours) by sintering at 140$0^{\circ}C$ and 150$0^{\circ}C$. The micrographs of grains showed an agglomeration and the degree of agglomeration increased with the milling time. The LaAlO$_3$ made from synthesized powders milling for 50 hours can be sintered to 99.5％ of theoretical density at 150$0^{\circ}C$ for 1 hour. These ceramics exhibits a dielectric constant of 20, a dielectric loss of 0.0003 and a temperature coefficient of capacitance of 15 ppm/$^{\circ}C$ at 1 MHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.648-651
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• 2003

Fine $LaAlO_3$ powders were successfully synthesized from $La_2O_3$ and ${\gamma}-Al_2O_3$ powders milling for $10{\sim}50hrs$ via the high energy milling technique (mechanochemical methode) in room temperature and air. The particle size of $LaAlO_3$ powder were estimated from XRD patterns and SEM images to be $160{\sim}180nm$. The $LaAlO_3$ ceramics are derived for the synthesized powders (milling for 10, 30 and 50hrs) by sintering at $1400^{\circ}C$. The micrographs of grains showed a agglomeration and the degree of agglomeration increased with the milling time. The $LaAlO_3$ made from synthesized powders milling for 30hrs can be sintered to 98% of theoretical density at $1,400^{\circ}C$ for 4hrs.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.58-65
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• 2005

The $LaCrO_3$-dispersed Cr alloys for metallic interconnect of solid oxide fuel cell were prepared as a function of $LaCrO_3$ content in the range of 5 to 25 vol.% and were sintered at 1500$^{\circ}C$ under an Ar atmosphere with 5 vol.% $H_2$. The sintering and oxidation behaviors of these alloys were examined. The alloys indicated a good sinterability above 95% relative density at a given sintering condition, and their sintering densities is independent on $LaCrO_3$ content. The $LaCrO_3$ particles of the sintered alloys were concentrated on interfaces of Cr particles, and the size of the Cr particles increased with decreasing $LaCrO_3$ content, which is caused by inhibited grain growth of Cr particle by $LaCrO_3$ particle. The oxidation test showed all $LaCrO_3$-dispersed Cr alloys have good oxidation resistance as compared with pure Cr, which is attributed to presence of $LaCrO_3$ at the interface at which the oxidation reaction occurs rapidly. The Cr alloys with about 15 vol.% $LaCrO_3$ are very resistant to oxidation.