X-ray powder diffraction data and refined unit cell parameters for three compounds found during experimental determination of the BaO:Fe2O3:TiO2 phase diagram are reported here. All three phases crystallize in space group C2/m (No. 12). Ba2Fe2Ti4O13 (“2:1:4”) is isostructural with K2Ti6O13 and Ba2ZnTi5O13: a=15.1939(9), b=3.8912(3), c=9.1244(5) Å, β=98.456(5)°; Z=2, ρcalc=4.890 g/cc. Ba3Fe10TiO20 (“3:5:1”) is structurally analogous to its aluminum congener Ba3Al10TiO20: a=15.336(1), b=11.7986(9), c=5.1700(4) Å, β=91.220(6)° (I2/m setting); Z=2, ρcalc=4.750 g/cc. Ba4Fe2Ti10O27 (“4:1:10”) is also isostructural with its aluminum analog Ba4Al2Ti10O27: a=19.799(1), b=11.4324(6), c=9.8936(6) Å, β=109.146(4)° (C2/m); Z=4, ρcalc=4.934 g/cc. The 2:1:4 and 3:5:1 compounds adopt open-framework type structures while the 4:1:10 phase exhibits an eight-layer close-packed arrangement.

It is known that solids with composition Na3Zr2Si2PO12 heated at 1200 °C crystallize in the nasicon structure. This material shows a high ionic conductivity that represents an interesting improvement in the field of solid electrolytes. Our experimental results allow to establish for the first time that nasicon structures are stable along the compositional join Na3Zr2−x/4Si2−xP1+xO12 with x extending from 0 to 1.667. These structures are characterized by a Zr underoccupation of octahedral sites and a constant number of Na+ ions. This fact envisages a possible application of these materials in the field of ceramic sensors and ionic conductors.

The crystal structures of solution-grown and melt-grown polycrystalline samples of n-hexatetracontane (n-C46H94) in the temperature range 293–359 K have been investigated by X-ray powder diffraction. The solution-grown sample has an orthorhombic structure, with space group Pbc21 and cell dimensions a=4.952 Å, b=7.424 Å, and c=120.95 Å. While heating this sample a gradual transition to a monoclinic phase takes place, with onset temperature 335 K. At temperatures close to the melting point two configurations of the ab plane have been observed. Cooling a sample from the melt results in a mixture of a monoclinic and an orthorhombic structure. Rietveld refinements of the structures of solution-grown and melt-grown samples at 293 K have been performed.

An in situ high pressure study using energy dispersive X-ray diffraction has been carried out on the polycrystalline high-Tc superconductor, HgBa2CuO4+δ (Hg-1201), to study its phase stability under pressure and also to measure its compressibility and bulk modulus. No evidence of pressure-induced polymorphism was found in the pressure range investigated, i.e., from 0.1 MPa (1 atm) to 5 GPa. The compound exhibited anisotropic elastic properties. The axial compressibility along the c axis was measured to be (3.96±0.35)×10−3GPa−1 and along the a axis (3.42±0.13)×10−3GPa−1, corresponding to an anisotropy ratio of 1.16±0.11. The bulk modulus was determined to be (94.7±4.2) GPa and, assuming a Poisson's ratio of 0.2, Young's modulus was estimated to be (170±8) GPa.

X-ray diffraction data has been collected from biological calcific mineral associated with human bone, breast tissue, ureteric calculi, heart valve, and aorta. All the materials are shown to have a nominal calcium hydroxyapatite structure and Rietveld analysis has been performed to extract microstructural information. All refinements achieved a final Rwp value of <10%. The lattice parameter ranges are a=9.375(3)(breast)−9.4316(8)(heartvalve), c=6.866(1)(uretericcalculi) −6.899(1)(rib), and crystallite size range from 40 Å (breast) to 99 Å (ureteric calculi). A correlation between crystallite size estimates from this Rietveld analysis and line profile methods is demonstrated. The results are supported by an infrared study and previous data from alternative techniques. Thus, it is demonstrated that the microstructure of these materials may be characterised by application of the Rietveld method.

A new occurrence of the poorly characterized mineral, yukonite, (Ca6.44K0.13Mg0.23)(Fe14.68Al0.36)(AsO4)9O15.78·25.5H2O, is described. New powder X-ray diffraction and electron microprobe data are provided for type material from Tagish Lake, Yukon Territory, Canada, and that from the new locality, Saalfield, Thuringen, Germany. New chemical formulae are proposed. The strongest reflections are at 14.1(100), 2.79(60), 3.25(57), 5.58(37), 2.61(20), 1.63(20), and 2.24(11) Å.

The thermal decomposition of barium bis(citrato)oxotitanate citrate heptahydrate, a molecular precursor of BaTiO3 fine powders is studied by temperature-dependent x-ray powder diffraction and thermogravimetry. A thorough investigation of the dehydration stage is presented. Three crystalline phases containing seven, three, and two water molecules, respectively, are identified from their powder diffraction pattern. The results of pattern indexing are presented and discussed in terms of parameter relationships.

X-ray powder diffraction data and refined unit cell parameters for SrTi3Nb4O17, SrTi5Nb4O21, SrTi7Nb4O25, SrTi9Nb4O29, SrTi11Nb4O33, SrTi13Nb4O37, and SrTi15Nb4O41 are reported here. The powder patterns for these oxides suggest that they form a homologous series SrM2n+1O4n+5 (M=Ti, Nb; n=3→9), which is isostructural with the orthorhombic “chemically twinned rutile” series found previously in the K2O-TiO2-Ta2O5 and BaO-TiO2-Nb2O5 systems. The structures are built of corner-sharing slabs of the rutile structure; successive members are generated by adding 2TiO2 to the slab thickness of the previous member. The series crystallizes in space group Cmcm (No. 63), with members exhibiting similar a-, b-dimensions (∼6.6, ∼8.9 Å; respectively), and c-dimensions that linearly increase (by ∼4.4 Å per member) from 20.8 Å for n=3 to 47.1 Å for n=9.