Structural investigations of polycrystalline diaspore samples by X-ray powder diffraction

X-Ray Powder Diffraction Rietveld Characterization of Synthetic Aluminum-Substituted Goethite

“…Table 4. Comparison ofx and y parameters for Fe/A1, O~, and 02 with values of Forsyth et al (1968) for goethite, and of and Klug and Farkas (1981) The results demonstrate the value of using Rietveld analysis to determine simultaneously the WFCM and AI mole % substitutions as well as to confirm the nonhydrogen atom positions.…”

“…The crystal structure model placed all atoms in the Wyckoff 4c positions of orthorhombic space group Pbnm having coordinates _(x, y, 0.25; 0.5 + x, 0.5 -y, 0.75). The x and y parameters for Fe/A1, O~, and 02 in the 8% material were refined commencing with the mean values for the parameters reported by Klug and Farkas (1981). The positional coordinates for the hydrogens were fixed at the means of the neutron diffraction values of Busing and Levy (1958), x = 0.412 and y = 0.088 and of Forsyth et al (1968), x = 0.399 and y = 0.088.…”

“…The positional parameters in Table 2 are compared in Table 4 with the values reported by and Klug and Farkas (1981) for diaspore and by Forsyth et al (1968) for goethite. The results do not indicate structural heterotypism within the set of three goethite specimens if esd's are considered.…”

Synthesis of Gallium Oxide Hydroxide Crystals in Aqueous Solutions with or without Urea and Their Calcination Behavior

“…On the other hand, the little and big zeppelins formed in the ureacontaining precipitation solutions also had the same XRD trace, with the same relative intensity values. The crystal structure presented by both kinds of gallium oxide hydroxide crystals was found to be analogous to the structure of diaspore, i.e., ␣-AlOOH, 27,28 and the space group of the diaspore structure is regarded to be Pbnm (62). Goethite and groutite (i.e., ␣-MnOOH 31 ) are also structurally similar to diaspore.…”

“…Precipitation of GaO(OH) in solutions containing dissolved gallium chloride, on the addition of various alkalis (such as NaOH, KOH, NH 4 OH, NaHCO 3 , and Na 2 CO 3 ), has been studied by Sato et al 26 These authors reported that the freshly precipitated (at pH values varying between 6 and 10) precursors were all X-ray amorphous 26 and converted to crystalline ␣-GaO(OH), with an orthorhombic crystal structure similar to that of diaspore (␣-AlO(OH)), 27,28 only after about 1 day of aging in their basic mother liquors. Pokrovski et al 29 determined the thermodynamic properties of ␣-GaO(OH), at temperatures up to 700 K, by using low-temperature heat capacity and solubility tests, and their data confirmed that gallium oxide hydroxide was the stable phase in the Ga-O-H system up to 300°C.…”