CeO2 transforms to an orthorhombic PbCl2-type structure at a pressure of about 31 GPa. The phase transition is accompanied by a 9.8% volume contraction. The bulk modulus of the low-pressure fluorite-type structure is 236(4) GPa. Comparisons are made with the high-pressure behaviour of UO2 and ThO2.

The crystal structure of α-CoSO4 has been refined by the Rietveld method from X-ray powder diffraction data. The structure is orthorhombic, space group Pnma, a = 8.6127(4), b = 6.7058(3), c = 4.7399(2) Å, V = 273.75(3) Å3. Final RB = 2.41%, RP = 5.24%, RWP=6.66%, RWP (expected) =5.74% (WP =weighted profile). The structure consists of edge-sharing octahedral chains parallel to [010] interconnected by SO4 tetrahedra.

Indexed X-ray powder diffraction data are reported for two organic salts with carbon rings having two quaternary nitrogens: diazonia-6,9 dispiro [5.2.5.2] hexadecane and diazonia-6,9 dispiro [5.2.5.3] heptadecane diiodides. For these compounds, which give solid electrolytes when associated with AgI, powder diffraction diagrams calculated by the Rietveld method from single crystal structure determinations are presented and are compared to the experimental diffraction data.

Powder diffraction data for semiconductor and metallic states of vanadium dioxide are presented. The structures are refined by Rietveld methods using a monoclinic cell (a = 5.7529Å, b = 4.5263Å, c = 5.3825Å, β = 122.61°) and space group P21/c for the room temperature data, and a tetragonal cell (a =4.5540Å, c = 2.8557Å) and space group P42/mnm for data collected at 400 K. The similarity between the corresponding X-ray diffraction patterns is discussed. The transition process from the monoclinic to tetragonal phase is investigated and initial evidence for the coexistence of phases over a small temperature range is presented.

The structure of pyrochlore type Y2Sn2O7 has been refined by Rietveld analysis from 1.4925 Å neutron powder diffraction data collected at 295 K and containing 46 independent reflections. The refinement figures of merit were Rp = 0.041, Rwp = 0.055, Rexp = 0.039, and RB = 0.006. The structure is a pyrochlore type, space group (S.G.) with a = 10.3723(1) Å, Dx = 6.21 g cm−3, and with the oxygen position parameter of 0.33694(5). The Sn atoms are in a nearly regular octahedral coordination whereas the Y has a distorted 8-fold coordination geometry. The anisotropic thermal parameters were also determined. The refined model has been used to calculate a set of d-I X-ray data for search/match analysis.

A new compound [Mn(H2O)]0.25(VO)0.75PO4·2H2O was prepared by the reaction of V2O5 with the boiling aqueous solution of H3PO4 and KMnO4. The reaction product is a yellow-brown powder, stable in air. The tetragonal unit-cell parameters (298 K) are a = 6.2034(2)Å, c = 13.814(1)Å, V = 531.59Å3, Z = 4, Mr = 194.94, Dx = 2.493 g/cm3, Dexp = 2.52 g/cm3. X-ray (CoKα radiation) powder diffraction data (35 lines) are reported. The compound's structure is probably derived from the VOPO4·2H2O layered lattice by substitution of [Mn(H2O)]3+ ions for a quarter of the vanadyl groups VO3+. Practically the same powder data and unit-cell parameters were found for [Mn(H2O)]x(VO)1−xPO4·2H2O, where x ranges from 0.185 to 0.25.

With a new emphasis on the control of polymorphism in pharmaceutical production, the need for methods to quantify polymorphic forms has arisen. Techniques using X-ray powder diffraction are increasingly being used to characterize the phases of drug substances that exist in multiple crystal forms. Current methods to identify the polymorphic phases in a drug substance include microscopy, infrared spectroscopy, thermal analysis (DSC/TGA), solid state NMR, and X-ray powder diffraction. Of the aforementioned techniques, X-ray powder diffraction provides the most effective approach to identify and quantify the different crystal phases of a pharmaceutical compound. This work is intended as a guide to the characterization and quantification of an organic crystalline system using X-ray diffraction. The approaches suggested are intended to provide assistance not only from an in-process pharmaceutical manufacturing standpoint, but also for routine quality assurance screening of polymorphic drug substances.

Ceric caesium nitrate CeCs2(NO3)6 and ceric rubidium nitrate CeRb2(NO3)6 have been investigated by means of X-ray powder diffraction. Precise data collected with strictly monochromatic radiation (CuKα1) are reported. Monoclinic unit cell dimensions were found by the indexing program DICVOL91 based on the variation of parameters by successive dichotomy. The final refined parameters are: a = 13.5373(7) Å, b = 7.0787(5) Å, c = 8.1672(5) Å, β = 90.813(5)° for the caesium compound and a = 13.0567(5) Å, b = 6.8684(2) Å, c = 8.1786(3) Å, β = 91.436(4)° for the rubidium compound, and the indexings are characterized by the figure of merit F30 equivalent to 245 (0.0033,37) and 194 (0.0040,39), respectively.

The title compounds crystallize in the cubic space group Fd3m, Z = 8, with cell parameters of 8.2958(37) Å for NiFeGaO4 and 8.3921(24) Å for ZnFeGaO4. By comparison of experimental and calculated patterns with various site distribution models, ZnFeGaO4 has been determined to have the normal spinel structure and NiFeGaO4 a dominantly inverse spinel structure.

An Sb3Nb3O13 [Sb(III)2Sb(v)Nb(v)3O13] phase having a defect pyrochlore structure has been prepared by heating a sol–gel derived powder in oxygen. X-ray powder diffraction results indicate that Sb3Nb3O13 has a face-centered cubic structure, S.G. Fd3m(227), with a refined unit cell parameter a =10.4965(1) Å, calculated density Dx=4.893, four molecules per unit cell (Z), and a calculated figure of merit SS/FOM F30=92.4(0.009,38).

A new high temperature form of Y2O3 has been synthesized at 2220 °C by a laser beam heating technique. The new form has a face-centered cubic structure with a = 5.2644(3)Å, Z = 2, Dx = 5.14 g/cm3, and is considered to have a fluorite-type structure containing disordered oxygen vacancies.

The X-ray powder diffraction pattern for a sample of the high-temperature superconducting phase Tl0.5Pb0.5Sr2CaCu2O6.5+δ has been determined. The sample was prepared by a molten salt technique and had a Tc of 96 K.

Substituting cations in materials with the formula Pb2B′B″O6 is more or less ordered on the B sites. High-quality single crystals of Pb2ScTaO6 (PST) and Pb(Sc0.5Nb0.5)O3 (PSN) were prepared from two thermal cycles. A stoichiometric mixture of the constituent oxides was prefired at up to 1000 °C, and then crystals were grown from a PbO–B2O3–PbF2 flux mixture, starting at a temperature of 1100 °C for PSN and 1200 °C for PST. At room temperature, X-ray examination showed that PSN had a perovskite structure with a cubic unit-cell and a refined parameter a = 4.080(1 ) Å, space group Pm3m and Z = 1, whereas PST formed a well-ordered superlattice with a = 8.136(1) Å, Z = 4 and space group Fm3m. In each case a fully indexed powder pattern is presented. The degree of order is estimated to be close to 80% for PST and less than 10% for PSN.

Schlippe's salt (sodium thioantimonate nonahydrate—Na3SbS4·9H2O) has been investigated by means of X-ray powder diffraction at room temperature. The indexed X-ray powder diffraction data are presented.

The title compound was synthesized by high temperature reaction of the component elements. This phase, formerly classified in the group of Nowotny phases, crystallizes in the hexagonal system with space group P63/mcm. Crystal data and indexed X-ray powder diffraction data are reported.

Indexed experimental powder diffraction patterns of Tl,Pb-1223 and Tl-1223 are presented with a method of determining good cell parameters for the former awkward case where c/a almost exactly equals 4. For Tl,Pb-1223, a = 3.814±0.001 Å, c = 15.267±0.005 Å, for Tl-1223, a = 3.814±0.001 Å, c = 15.302±0.005 Å, both tetragonal, space group P4/mmm.