Lattice Modulation in the Long Period Ordered Alloys Studied by X-Ray Diffraction. III. : Cu_3Pd(α")

Periodic atom displacements in the long period ordered alloy Cu_3Pd(α") with the one-dimensional anti-phase domain structure have been investigated by X-ray diffraction using an alloy single crystal. It has resulted from the crystal structure analysis, that in Cu_3Pd(α") the heavier atoms (palladium) are displaced toward the anti-phase boundary and the lighter atoms (copper) away from it, giving rise to puckered planes. These behaviors are different from those of Au_3Cd and CuAuII in which the heavier atoms are displaced away from the boundary and the lighter atoms toward it. Thus, the atom displacements are affected by the kind of alloys. A little disordering is present in atomic sites in the mixed plane facing the boundary

Amorphous Phase in Yttrium-Cobalt-Boron System

By rapid quenching of the melt, an amorphous phase of yttrium-cobalt-boron system was obtained. The phase is stable at room temperature, and its crystallization takes place in the vicinity of 700℃ on heating at 10℃/min. Electrical resistivity of the amorphous phase is constant at about 10^Ωcm in the temperature range below 660℃ ; the variation in the resistivity with the transition from the amorphous to the equilibrium state was measured

3Gd_2O_3・5Fe_2O_3 Glass Obtained by Rapid Quenching Apparatus Using Laser Beam

The oxide glass of 3Gd_2O_3・5Fe_2O_3 (GIG) was prepared using the piston and anvil technique incorporated into a laser melting furnace. The quenching apparatus provides higher quenching rates than an impact quenching apparatus already made. Crystallization and magnetization of the GIG glass have been examined by means of DTA method and magnetic balance

Crystallization of 3Ln_2O_3・5Ga_2O_3 Glasses

The oxide glasses of 3Ln_2O_3・5Ga_2O_3 Were prepared, using Pr, Nd, Sm, Eu or Gd as a lanthanoid element . Crystallization of the glasses was studied by DTA and X-ray diffraction. A metastable phase was found on the way of the crystallization process of 3Pr_2O_3・5Ga_2O_3 and 3Nd_2O_3・5Ga_2O_3 glasses terminating in the transition into garnet. However, the phase transition transforming the amorphous phase directly into garnet not through a metastable phase was observed in case of 3Ln_2O_3・5Ga_2O_3 glasses (Ln=Sm, Eu or Gd)

Unusual Glass Formation in the Al-Nd-O System

A new oxide glass in the Al-Nd-O system was made through fusing by arc plasma torch and rapid quenching by a particular device although, in this system, so far it was very difficult to realize the glassy state. Quenched material of about 5 mm in diameter and about 1 μ in thickness was examined by polarizing microscope and by X-ray diffraction technique. The results clearly showed the existence of the glassy state

Lattice Modulation in the Long Period Ordered Alloys Studied by X-Ray Diffraction. II : CuAuII

The crystal structure of the long period ordered alloy CuAuII has been investigated by X-ray diffraction using an alloy single crystal with the composition of Cu-50 at.%Au. Half of the long period of the alloy has been measured to be 5.0 in units of the fundamental L1_0-type cell, differing from the result of Jehanno and Perio on a polycrystalline alloy. The Fourier synthesis has been made using H, K, 0 type reflections recorded on Weissenberg photographs. Taking into account the information obtained from the synthesis, the structure parameters including atomic coordinates, temperature factor and occupancy ratio of each atomic site have been refined by a modified least squares method. It has been confirmed that atoms are periodically displaced from the normal lattice points of the fundamental cell. Copper atoms shift by distances ranging from 0.079A to 0.028A toward the anti-phase boundary and gold atoms by distances ranging from 0.048A to 0.004A in the opposite direction. The atomic disordering occurs considerably in the neighborhood of the anti-phase boundary, while it is not much in the center of the antiphase domain

Synthesis of Lanthanoid Aluminates (β-Al_2O_3 Type) Using Arc Plasma Flame

New compounds with approximate formulas, La_2O_3・7Al_2O_3, Pr_2O_3・7Al_2O_3, Nd_2O_3・8Al_2O_3 and Sm_2O_3・7Al_2O_3, have been obtained through melting by arc plasma flame and separated into their own single phases by a proper chemical treatment. All of the compounds have the β-Al_2O_3 type structure. Excepting only La_2O_3・7Al_2O_3, these compounds have the β-Al_2O_3 type structure at temperatures higher than 1500℃

Crystallization of an Amorphous Oxide in La-Nb-O System

An amorphous oxide of which composition corresponds to La_2O_3・5Nb_2O_5 was prepared by making use of an impact quenching technique. The phase transformation from an amorphous to an equilibrium crystalline state was studied by means of differential thermal analysis (DTA) and X-ray diffraction. From the experimental results, the crystallization process was characterized mainly by the two successive transitions, i.e., glassy phase → a new metastable phase → stable phase of La_2O_3・5Nb_2O_5

Glass Formation in the Ln-Al-O System (Ln : Lanthanoid and Yttrium Elements)

Oxide glasses in the Ln-Al-O system were prepared with the molar ratio of Ln_2O_3 : Al_2O_3 of 10 : 1 to 1 : 10 for all the lanthanoids and yttrium by an impact quenching technique. Each quenched material was examined by polarizing microscope, X-ray diffraction and electron diffraction. The electron diffraction patterns show diffuse halos characteristic of an amorphous state

Raman Scattering of Inorganic Fibers

We have examined evolution of Raman spectra of carbon fibers and SiC fibers through structural transformations caused by heat treatment. Raman spectra of the SiC fibers indicate that the fibers consist of amorphous or microcrystalline SiC and graphitic microcrystals. We discuss the correlation between the tensile strength of the fibers and their microscopic structure deduced from the Raman data