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Journal Articles

In situ transmission electron microscopy observation of melted germanium encapsulated in multilayer graphene

Suzuki, Seiya; Nemoto, Yoshihiro*; Shiiki, Natsumi*; Nakayama, Yoshiko*; Takeguchi, Masaki*

Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09

https://doi.org/10.1002/andp.202300122

Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)

Journal Articles

Phase-field mobility for crystal growth rates in undercooled silicates, SiO and GeO liquids

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of Crystal Growth, 585, p.126590_1 - 126590_7, 2022/05

https://doi.org/10.1016/j.jcrysgro.2022.126590

Phase-field mobility, , and crystal growth rates in crystallization of 11 oxides or mixed oxides in undercooled silicates, SiO and GeO liquids were calculated with a simple phase-field model (PFM), and material dependence of the was discussed. Ratios between experimental crystal growth rates and the PFM simulation with were confirmed to be proportional to a power of $frac{TDelta T}{eta}$ on the solid/liquid interface process during the crystal growth in a log-log plot. We determined that parameters, and , of the $L=A(frac{k_{B}TDelta T}{6pi^{2}lambda^{3}eta T_{m} })^{B}$ were $A=6.7times 10^{-6}$ to mJ $^{-1}$ s $^{-1}$ and to , which were unique for the materials. It was confirmed that our PFM simulation with the determined reproduced quantitively the experimental crystal growth rates. The has a proportional relationship with the diffusion coefficient of a cation molar mass average per unit an oxygen molar mass at $T_{m}$ in a log-log graph. The depends on the sum of the cation molar mass per the oxygen molar mass, $frac{Sigma_{i}M_{i}}{M_{O}}$ , in a compound. In $frac{Sigma_{i}M_{i}}{M_{O}}leq 25$ , the decreases with the cation molar mass increasing. The assumed cause is that the B represents the degree of the temperature dependence of the . Since the cation molar mass is proportional to an inertial resistance of the cation transfer, the decreases with inverse of the cation molar mass. In crystallization of the silicates of heavy cation in $frac{Sigma_{i}M_{i}}{M_{O}}geq 25$ , the saturates at approximately 0.67, which leads to $T_{p}approx 0.9T_{m}$ .

Journal Articles

Phase-field model for crystallization in alkali disilicate glasses; LiO-2SiO, NaO-2SiO and KO-2SiO

Kawaguchi, Munemichi; Uno, Masayoshi*

Journal of the Ceramic Society of Japan, 128(10), p.832 - 838, 2020/10

https://doi.org/10.2109/jcersj2.20145

Times Cited Count：2 Percentile：16.44(Materials Science, Ceramics)

This study developed phase-field method (PFM) technique in oxide melt system by using a new mobility coefficient (). The crystal growth rates () obtained by the PFM calculation with the constant were comparable to the thermodynamic driving force in normal growth model. The temperature dependence of the was determined from the experimental crystal growth rates and the . Using the determined , the crystal growth rates () in alkali disilicate glasses, LiO-2SiO, NaO-2SiO and KO-2SiO were simulated. The temperature dependence of the was qualitatively and quantitatively so similar that the PFM calculation results demonstrated the validity of the . Especially, the obtained by the PFM calculation appeared the rapid increase just below the thermodynamic melting point ( $T_{rm m}$ ) and the steep peak at around $T_{rm m}$ -100 K. Additionally, as the temperature decreased, the apparently approached zero ms, which is limited by the representing the interface jump process. Furthermore, we implemented the PFM calculation for the variation of the parameter in the . As the increased from zero to two, the peak of the became steeper and the peak temperature of the shifted to the high temperature side. The parameters and in the increased exponentially and decreased linearly as the atomic number of the alkali metal increased due to the ionic potential, respectively. This calculation revealed that the and in the were close and reasonable for each other.

Journal Articles

Spectroscopic properties of Yb doped YLF grown by a vertical Bridgman method

Sugiyama, Akira; Katsurayama, Masamichi*; Anzai, Yutaka*; Tsuboi, Taiju*

Journal of Alloys and Compounds, 408-412, p.780 - 783, 2006/02

https://doi.org/10.1016/j.jallcom.2005.01.094

Times Cited Count：24 Percentile：75.19(Chemistry, Physical)

Laser crystals of LiYF $_{4}$ (YLF) doped with 5 - 64 at.% of trivalent ytterbium ions (Yb $^{3+}$ ) were grown by a vertical Bridgman method. As crystal growth materials of YbF $_{3}$ and YF $_{3}$ including YOF impurities caused opaque crystal, the YOF reduction procedure using PbF $_{2}$ was essential before starting the crystal growth. We derived seven energy levels from the $^{2}$ F $_{7/2}$ and $^{2}$ F $_{5/2}$ manifolds of Yb $^{3+}$ : YLF by the crystal-field analysis from which we explain the observed polarized absorption and emission spectra. The intrinsic broad and complicated spectra of Yb $^{3+}$ : YLF are attributed to the strong coupling of the 4f electrons with lattice vibration of the crystal.

Journal Articles

Small saturation moment due to the crystalline electric field effect for site symmetry in the ferromagnet UFeP $_{12}$

Matsuda, Tatsuma; Galatanu, A.; Haga, Yoshinori; Ikeda, Shugo; Yamamoto, Etsuji; Hedo, Masato*; Uwatoko, Yoshiya*; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Kindo, Koichi*; et al.

Journal of the Physical Society of Japan, 73(9), p.2533 - 2538, 2004/09

https://doi.org/10.1143/JPSJ.73.2533

Times Cited Count：8 Percentile：48.25(Physics, Multidisciplinary)

Electrical resistivity, specific heat, magnetic susceptibility and high-field magnetization measurements have been performed on the ferromagnet UFe $_{4}$ P $_{12}$ with the cubic crystal structure. The ferromagnetic ordering at $T_{rm C}$ ,=,3.1 K, a small saturation moment of 1.3 $mu_{rm B}$ /U, together with the temperature dependence of the magnetic susceptibility, are found to be well explained by considering the 5 crystalline electric field schemes for $T_{h}$ site symmetry and the magnetic exchange interaction.

Journal Articles

Effects of ultrastrong gravitational field on the crystalline state of a Bi-Sb alloy

Huang, X.*; Mashimo, Tsutomu; Ono, Masao; Tomita, Takeshi; Sawai, Tomotsugu; Osakabe, Toyotaka; Mori, Nobuo*

Journal of Applied Physics, 96(3), p.1336 - 1340, 2004/08

https://doi.org/10.1063/1.1763236

Times Cited Count：11 Percentile：42.73(Physics, Applied)

Mega-gravity field experiments were performed on the Bi $_{70}$ Sb $_{30}$ (atomic percent) alloy and pure Bi below their melting points, to investigate the change in crystalline state. For the alloy centrifuged at 191-205 $^{circ}$ C, no change in composition was observed, and the grain sizes of the crystals decreased from several mm to tens of m, while no distinct change in grain size was observed for the centrifuged pure Bi. The alloy centrifuged at 220-240 $^{circ}$ C consisted of two regions with different morphologies-fine-grained crystals with grain sizes around tens of m in the low gravity region, and large crystals with grain sizes several mm long and hundreds of m wide along the direction of gravity in the high gravity region, where sedimentation of atoms was confirmed. The large crystals with hexagonal structures were formed by preferential crystal growth roughly along the c axes, and a large strain that increased as the gravitational field increased existed inside these crystals. Formation of this anomalous crystal state might be correlated with the sedimentation of atoms.