Indexed X-ray powder diffraction data are reported for the semiconducting compound Ba2Cl2Cu3O4. The structure was refined by the Rietveid technique on the basis of the space group I4/mmm. Refined unit cell dimensions are a = 5.5156(1) Å, c = 13.8221(3) Å, V = 420.49 Å3Dx = 4.74 g/cm3, F30 = 129(0.0075,30), M20 = 121, Rp = 6.58, Rwp = 8.66, and RB = 4.49.

Measurements of X-ray diffraction patterns of high-Tc superconductor and tungsten–carbide powder samples using a Bragg–Brentano diffractometer showed systematic variations of the intensities for different preparation conditions. For specimens with high surface roughness, an angle-dependent decrease of the intensities is observed which is caused by the microabsorption of the X-rays due to the microstructure of the powder sample. In Rietveld analysis, the thermal parameters are strongly influenced by this effect and may tend to negative values. A realistic description of the surface structure of flat powder samples is proposed. Using an analytical approximation for the microabsorption effect and its dependence on the microstructural parameters the Rietveld refinement yields reasonable values for the thermal parameters.

Surface roughness of planar samples causes an additional attenuation of X-ray diffraction intensity measured in Bragg–Brentano geometry. The decrease of intensity becomes stronger with decreasing scattering angle. This is part of the microabsorption effect. Two quantitative expressions describing the microabsorption effect are incorporated into the DBWS 9006-PC Rietveid program [D. B. Wiles and R. A. Young, J. Appl. Crystallogr. 15, 149–151 (1981)]. The procedure is applied to scattering data obtained from YBa2Cu3O7-powder samples with different degree of surface roughness but approximately identical bulk structure. The procedure is proved to work well. However, the values obtained for the parameters of the temperature factors and the microabsorption effect are correlated, and careful discussion is necessary to interpret the results.

The phase decomposition occurring during the heating of rapidly quenched Al–Ge–Si alloys has been investigated in situ by means of synchrotron radiation X-ray diffraction. The metastable Al–Ge phases formed in the as-quenched state transform during heating to Al and Ge. The addition of silicon decreases the transformation temperature. A Ge(Si) solid solution is indicated by a systematic change in the lattice constant of Ge as a result of the diffusion of Si from the Al matrix into the phase-separated Ge matrix.

The structural evolution of the Ti40Zr10Cu34Pd14Sn2 bulk metallic glass (BMG) upon was investigated by means of in situ high-energy x-ray diffraction. The position, width, and intensity of the first peak in diffraction patterns are fitted through Voigt function below 800 K. All the peak position, width, and intensity values show a nearly linear increase with the increasing temperature to the onset temperature of structural relaxation, Tr = 510 K. However, these values start to deviate from the linear behavior between Tr and Tg (the glass transition temperature). The changes in free volume and the coefficient of volume thermal expansion prove that the aforementioned phenomenon is closely related to the structural relaxation releasing excess free volume arrested during rapid quenching of the BMG. Above 800 K, three crystallization events are detected and the first exothermic event is due to the formation of metastable nanocrystals.

The phase formation of a Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5alloy has been investigated upon cooling from the melt at different quenching rates as well as upon annealing of as-cast specimens. The different samples are characterized by x-ray diffraction, transmission electron microscopy and differential scanning calorimetry. Rapid quenching using the melt spinning technique results in amorphization. Slower cooling as realized upon copper mold casting leads to an icosaheadral quasicrystalline phase coexisting with a small amount of amorphous phase. The primarily formed quasicrystals have a grain size of about 1 νm. Upon annealing, the amorphous phase formed upon melt spinning precipitates quasicrystals in the first step of a series of transformations to the crystalline equilibrium compounds. The quasicrystals formed by annealing do not exceed a size of 5 to 10 nm.

The effect of iron and oxygen additions on the thermal stability of rapidly quenched amorphous Zr65Al7.5Cu17.5Ni10) was studied by x-ray diffraction and differential scanning calorimetry. With increasing Fe content the glass transition temperature Tg and the crystallization temperature Tx shift to higher temperatures. The increase is more significant for Tg than for Tx, resulting in a decrease of the supercooled liquid region with increasing Fe content. For oxygen additions Tx decreases with increasing oxygen content whereas Tg increases slightly, causing a decrease of the supercooled liquid region with increasing oxygen content. The results reveal that even minor iron or oxygen contaminations lead to drastic changes in the glass transition behavior and the crystallization mode. Large iron or oxygen contents lead to the formation of nanocrystalline microstructures instead of coarse-grained material.