• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.824-828
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• 1990

Zirconia gel fibers were fabricated by sol-gel processing using zirconium alkoxides and 2, 4-pentanedione. Their phase transformation and microstructural evolution were studied after heat treatments up to 150$0^{\circ}C$. Tetragonal ZrO2 began to form at 50$0^{\circ}C$ and followed by monoclinic, tetragonal phase during subsequent heat treatments at 1000, 150$0^{\circ}C$ for 1hour respectively. During cooling from 150$0^{\circ}C$, cracks were created, propagated along grain boundaries due to the volume change from tetragonal to monoclinic transformation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.607-608
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• 2005

In this paper, author describe the undoped and $Co^{2+}$(0.5mole%) doped $Cd_4SnSe_6$ single crystals were grown by the chemical transport reaction(CTR) method. The grown single crystals crystallize in the monoclinic structure of space group Cc and have the direct band gap structure. The energy gaps of them are 1.68 eV for $Cd_4SnSe_6$ and 1.50 eV for $Cd_4SnSe_6:Co^{2+}$ at 300K respectively.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.835-839
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• 1995

Mer,trans-Re(≡NC6H5)(PPh3)2Cl3, Ⅰ, reacted with trimethylphosphine to give a mixture of two stereoisomers, mer,trans-Re(≡NC6H5)(PMe3)2Cl3,Ⅱ, and fac,cis-Re(≡NC6H5)(PMe3)2Cl3, Ⅲ. These compounds could also be prepared from the reaction of Re(≡NC6H5)(PMe3)(PPh3)Cl3 with trimethylphosphine. In both reactions the mer,trans-isomer is a major product. The products have been characterized by NMR, elemental analysis, and X-ray crystallography. Crystal data for Ⅱ: monoclinic space group P21, a=10.053(1) Å, b=10.844(1) Å, c=10.058(2) Å, β=113.45(2)°, Z=2, R(wR2)=0.0348 (0.0894). Crystal data for Ⅲ: monoclinic space group P21/n, a=7.183(2) Å, b=16.983(4) Å, c=15.543(4) Å, β=90.38(2)°, Z=4, R(wR2)=0.0603 (0.1484).

• Journal of the Korean institute of surface engineering
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• v.29 no.3
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• pp.176-185
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• 1996

플라즈마 용사된 열벽코팅의 수명을 평가하기 위하여 여러가지 양의 CeO$_2$(16,18,20,22,24 그리고 26 wt.% CeO$_2$)를 포함하는 지르코니아 코팅에 대한 상분석이 행하여 졌다. 플라즈마 용사된 후 16 및 18 wt.% CeO$_2$를 포함하는 지르코니아 코팅에서는 비평형 tetragonal 상 만이 생성되었으나 20-26 wt.% CeO$_2$를 포함하는 지르코니아 코팅에서는 비평형 tetragonal 및 cubic 상의 혼합상이 관찰되었다. 열순환 산화시험 동안에는 비평형 tetragonal 및 cubic 상은 평형 tetragonal 및 cubic 상으로 변태하였다. 평형 tetragonal 상의 일부는 열순환 산화시험의 냉각과정 중에 monoclinic 상으로 변태하였다. 그리고 16 wt.% CeO$_2$를 포함하는 지르코니아 코팅은 다른 조성의 지르코니아 코팅보다 열순환 산화시험 동안 더 많은 monoclinic 상이 생성되었으며 세라믹 코팅 수명이 짧았다.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.86-89
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• 2015

Uniform ZrO₂ nanoballs were synthesized at 700℃ using the inverse replication method through a colloid-imprinted carbon (CIC) template. The structural, dielectric, and conducting properties of the ZrO₂ nanoballs were investigated and compared with those of ZrO₂ film prepared by sol-gel method and powdered ZrO₂ chemical. Both the monoclinic and cubic phases were found in the ZrO₂ balls and film but the ZrO₂ chemical showed a monoclinic phase, where the cubic structure is known to be formed at above 2,300℃. ZrO₂ nanoballs showed the lower dielectric property of k = 21.2 at 1 MHz because the 8-coordinated cubic phase in the ZrO₂ nanoball produced lower polarization than the polarization of the 7-coordinated monoclinic ZrO₂ chemical (k = 23.6). The dielectric stability was maintained in each ZrO₂ ball, film, and chemical under the applied forward and reverse voltage range (−5 to +5 V) at 1 MHz. The ionic conductivities were 7.86 × 10⁻⁸/Ω·cm for ZrO₂ nanoballs, 3.29 × 10⁻⁸/Ω·cm for ZrO₂ chemical, and 6.70 × 10⁻⁵/Ω·cm for the thickness of 1,053 nm ZrO₂ film at room temperature with the electronic contribution being less than 0.006%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.2
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• pp.62-67
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• 2008

An Organometallic compound, $C_{12}H_{20}B_{10}S_2Co_2$, was synthesized from o-carborane, $Cp^*Co(S_2B_2B_{10}H_{10})$ and $BH_3{\cdot}THF$. The molecular structure of this complex has been determined by X-ray diffraction. Crystallographic data: monoclinic, space group Cc, a=15.981(4) ${\AA}$, b=15.478(17) ${\AA}$, c=12.0562(17) ${\AA}$, ${\beta}=115.063(16)^{\circ}$, Z=4, V=9683(4) ${\AA}^3$. The structure was solved by direct methods and refined by full-matrix leat-squares methods to give a model with a reliability factor R = 0.0630 for 9948 reflections.

• Korean Journal of Materials Research
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• v.23 no.6
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• pp.329-333
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• 2013

The structural phase transformations of $0.7Pb(Mg_{1/3}Nb_{2/3})O_3-0.3PbTiO_3$ (PMN-0.3PT) were studied using high resolution x-ray diffraction (HRXRD) as a function of temperature and electric field. A phase transformational sequence of cubic (C)${\rightarrow}$tetragonal (T)${\rightarrow}$rhombohedral (R) phase was observed in zero-field-cooled conditions; and a $C{\rightarrow}T{\rightarrow}$monoclinic $(M_C){\rightarrow}$ monoclinic ($M_A$) phase was observed in the field-cooled conditions. The transformation of T to $M_A$ phase was realized through an intermediate $M_C$ phase. The results also represent conclusive and direct evidence of a $M_C$ to $M_A$ phase transformation in field-cooled conditions. Beginning from the zero-field-cooled condition, a $R{\rightarrow}M_A{\rightarrow}M_C{\rightarrow}T$ phase transformational sequence was found with an increasing electric field at a fixed temperature. Upon removal of the field, the $M_A$ phase was stable at room temperature. With increasing the field, the transformation temperature from T to $M_C$ and from $M_C$ to $M_A$ phase decreased, and the phase stability ranges of both T and $M_C$ phases increased. Upon removal of the field, the phase transformation from R to $M_A$ phase was irreversible, but from $M_A$ to $M_C$ was reversible, which means that $M_A$ is the dominant phase under the electric field. In the M phase region, the results confirmed that lattice parameters and tilt angles were weakly temperature dependent over the range of investigated temperatures.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.762-766
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• 1999

The crystal structure of A2+(Mg1/3Nb2/3)O3,(A2+=Sr2+ and Ca2+)ceramics was studied usig X-ray diffraction (XRD) and high resolution transmission electrion microscopy(HRTEM). Ba(Mg1/3Nb2/3)O3 (SMN) has the 1:2 ordered monoclinic structure which has the anti-phase tilt of octahedra. The type of tilting in SMN was considered to be a$^{\circ}$a$^{\circ}$c- or a­a­c$^{\circ}$ Ca(Mg1/3Nb2/3)O3 (CMN) also has the 1:2 ordered monoclinic structure which was distorted by the anti-phase tilt or in-phsae tilt of octahedra. A unit cell containing both the in-phase tilt axis and anti-phase tilt axis was not observed in the CMN. Therefore CMN has the mixed phase consisting of the 1:2 ordered monoclinic phase with anti-phase tilt of octahedra and the one with in -phase tilt of ocatahedra,. The anti-parallel shift of cation was also observed in the CMN.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.83-88
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• 2019

LiBaPO₄:Eu²⁺ phosphors with stoichiometric and nonstoichiometric compositions were prepared using a solid state reaction followed by heat treatment in reduced atmosphere, and the crystal structures and photoluminescence(PL) properties of the powders were investigated by x-ray powder diffraction and luminescence spectrometer. At 900℃, the Ba₃(PO₄)₂ phase as the intermediate phase was observed with the LiBaPO₄ phase as the main crystalline phase. Samples with a low europium concentration at 1,000℃ belonged to the trigonal structure, whereas samples with Eu²⁺ content more than 4 mol% showed monoclinic structure. In the nonstoichiometric compositions of 4 mol% Eu²⁺ and above, a single phase of Eu²⁺-doped LiBaPO₄, showing bluish green emission, was formed.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.149-155
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• 1984

The effect of $ZrO_2$ dispersed phase on the mechanical properties in $Al_2O_3$-$ZrO_2$system has been studied. There are both metastable tetragonal phase and stable monoclinic phase of $ZrO_2$particles diespersed in Al2O3 matrix at room temperature. Metastable tetragonal $ZrO_2$ changes to the stable monoclinic structure within the stress field of the crack. And microcracks are formed by the expansion of $ZrO_2$during the tetragonal-monoclinic transformation on cooling. Therefore stress-induced phase transformation and inclusion-induced microcracking contribute to the mec-hanical properties of $Al_2O_3$-$ZrO_2$system. Sintered composites containing 10m/o $ZrO_2$ yield KiC values of 6.5MN/$m^{3/2}$ much greater than that of pure $Al_2O_3$ This increase results from microcrack extension and stress-induced phase transformation absor-bing energy by crack propagation. Flexural strength of composites is decreased considerably in comparison with pure $Al_2O_3$ This decrease results from microcrack as a crack former and higher porosity than pure $Al_2O_3$.