Kunio Kudou

Preparations and Some Properties of W2B, δ-WB and WB2 Crystals from High-Temperature Metal Solutions

W2B, δ-WB and WB2 crystals were prepared from high temperature aluminium and copper solutions using tungsten metal and crystalline boron powders as starting material under an argon atmosphere. Growth conditions for obtaining crystals of relatively large size were established. The crystals were examined by X-ray diffraction and chemical analysis. The Vickers microhardness and electrical resistivity of the crystals was measured, and oxidation at high temperature in air was studied. The microhardness value on (001) planes of δ-WB crystals is in the range of 25.3(±0.4)-26.7(±1.2) GPa. The microhardness value on (0001) planes of WB2 crystals is 21.3(±0.4) GPa. The electrical resistivity determined on δ-WB and WB2 crystals are as follows: for δ-WB: 171.5 µ Ω cm; for WB2: 312.6 µ Ω cm. The oxidation of W2B, δ-WB and WB2 crystals begins to proceed with a measurable rate in the temperature range 550-730° C. The final oxidation products contain WO3 and probably amorphous B2O3 or H3BO3.

Single-crystal growth and properties of CrB, Cr3B4, Cr2B3 and CrB2 from high-temperature aluminum solutions

Single crystals of CrB, Cr3B4, Cr2B3, and CrB2 were grown from high-temperature Al solutions. The crystals were examined by X-ray diffraction and chemical analysis. The CrB, Cr3B4, and Cr2B3 single crystals were obtained as columnar and thick-platelet crystals having well-developed (010) and (100) faces with maximum dimensions of 3 to 8 mm. CrB2 single crystals 4–8 mm in size were obtained as thick platelets having well-developed (0001) planes or as needles elongated in the 〈0001〉 direction. The Vickers microhardness and electrical resistivity of the crystals were measured, and oxidation at high temperature in air was studied.

Crystal growth by molten metal flux method and properties of manganese silicides

Abstract Crystals of binary manganese silicides were grown from high temperature copper, tin and lead metal fluxes by slow cooling method under an argon atmosphere. The growth conditions for obtaining single crystals of relatively large size were established. For tin and lead fluxes, the three silicides Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals were prepared, and Mn 5 Si 3 (about 0.1×0.1×6.4 mm 3 ) and MnSi (about 0.9×1.0×9.2 mm 3 ) were obtained of relatively large size from the tin flux. For copper flux, only the two silicides MnSi and Mn 5 Si 3 were formed, and the crystals were somewhat smaller. As-grown Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals were used for chemical analyses and measurements of density and unit cell parameters. The chemical analyses of the crystals are discussed. Vickers microhardness and electrical resistivity were determined on MnSi and Mn 5 Si 3 crystals, and oxidation at high temperature in air was studied for Mn 5 Si 3 , MnSi, and Mn 27 Si 47 crystals.

Single crystals of TaB, Ta5B6, Ta3B4 and TaB2, as obtained from high-temperature metal solutions, and their properties

Single crystals of TaB, Ta5B6, Ta3B4 and TAB2 of size 0.2-0.4 mm were prepared from high-temperature Al solutions. The crystals were examined by X-ray diffraction and chemical analysis. The Vickers microhardness of the crystals was measured and oxidation at high temperature in air was studied. The TaB, Ta5B6, and Ta3B4 single crystals were obtained as columnar crystals having well-developed {010} and {100} faces. The TaB2 single crystals were obtained as thick platelets with large {0001} planes. The Vickers microhardness of TaB, Ta5B6 and Ta3B4 single crystals measured in several directions on {010} planes ranges from 2330 to 2530 kgf mm-2. The microhardness value on the {0001} planes of TaB2 crystals is in the range of 2780 ~ 2960 kgf mm-2. The oxidation of TaB, Ta5B6, Ta3B4 and TaB2 crystals begins to proceed with a measurable rate in the temperature range 640-680°C. The final oxidation product is Ta2O5.

Synthesis and characterization of the nonstoichiometric perovskite-type compound ScRh3Bx

Abstract Polycrystalline samples of ScRh 3 B x (0≤ x ≤1.0) were synthesized by the arc melting method. The crystal structure is the perovskite-type cubic structure (space group Pm3m ) for boron content in the range 0≤ x ≤1.0 (0–20 at.% B). The lattice parameter a varies linearly from a =0.3903(1) nm ( x =0) to 0.40799(3) nm ( x =1.0). The micro-Vickers hardness increases with increasing boron content from 1.9 (±0.1) GPa for ScRh 3 (0 at.% B) to 9.9 (±0.1) GPa for ScRh 3 B 1.0 (20 at.% B). Thermogravimetric analysis indicates that the oxidation onset temperature for stoichiometric ScRh 3 B is 868 K. A sharp exothermic peak is observed at 1068 K by differential thermal analysis. The weight gain of the sample by heating in air up to 1473 K is 12.7%. The weight gain increases with increasing boron content. All samples in the range 0≤ x ≤1.0 show a metallic temperature dependence of the resistivity down to 0.5 K. Magnetic susceptibilities also show Pauli paramagnetic behavior and no trace of magnetic transitions on superconductivity in any of the samples.

Solid solution range of boron, microhardness and oxidation resistance of the perovskite type RERh3Bx (RE=Gd, Y, Sc) compounds

Abstract Polycrystalline samples of RERh 3 B x (RE=Gd, Y, Sc), which consists of a reactive RE and high melting point Rh and B elements, are successfully synthesized by the arc melting method. RERh 3 B x compounds have the perovskite type cubic structure (space group Pm 3 m ). Perovskite type phases of GdRh 3 B x and YRh 3 B x exist in the range of ∼0.444≤ x ≤1.000. On the other hand, phase of ScRh 3 B x exists in the range of 0≤ x ≤1.000 (0 to 20 mol% B). ScRh 3 , in the case of x =0, has AuCu 3 type structure; its space group is also Pm 3 m . The lattice parameter a in RERh 3 B x depends on x and the value of a increases with increasing boron content x . The value of Vickers microhardness of the RERh 3 B x at room temperature ranges from 6 to 10 GPa. According to thermo-gravimetric and differential thermal analysis for RERh 3 B x (RE=Gd, Y) heating up to 1200°C in air, a mixed phase of REBO 3 and Rh is identified as an oxidized product. In the case of ScRh 3 B, the oxidized product consists of Rh, Sc 2 O 3 and ScBO 3 .

First-principles study of the structural, electronic, and elastic properties of R Rh 3 B x C 1 − x ( R = Sc and Y)

We study the variation in the structural and electronic properties as well as bulk modulus of perovskite-type

Magnetic properties of thulium aluminoboride TmAlB4

R{\mathrm{Rh}}_{3}{\mathrm{B}}_{x}{\mathrm{C}}_{1\ensuremath{-}x}

Ab initio studies of structural, elastic, and electronic properties of RRh3BX (R=Sc, Y, La, and Ce)

with

Crystal Growth and Properties of AlLiB14

R=\mathrm{Sc}