X-ray powder diffraction analysis of samples obtained by thermal treatment of coprecipitated amorphous xCd(II) (1-x)Ni(II)2Fe(III)-hydroxides reveals that intermediate crystalline spinel species with lattice constants less than those for the nominal composition are formed before the designated cadmium-nickel ferrites, CdxNil-xFe2O4, come into existence.

Bright apple green millimeter-sized crystals of tavorite from the Tip Top pegmatite, near Custer, South Dakota are triclinic, space group , with refined unit-cell parameters a = 5.340(2), b = 7.283(2), c = 5.110(2)Å, α = 109.29(2)°, β = 97.86(3)°, γ = 106.32(3)°, V = 174.1(3)Å3, a:b:c = 0.7332:1:0.7016, Z = 2, D(m) (suspension in methylene iodide) = 3.32(1) and D(x) = 3.33 g/cm3 (for the theoretical formula). A fully indexed X-ray powder pattern is presented. Semiquantitative electron microprobe and secondary ion mass spectroscopic analyses indicate a formula near end-member LiFe + 3(PO4)(OH). The Tip Top tavorite is biaxial positive, α = 1.795(5), β = 1.81(1), γ = 1.86(1), 2V(meas.) = 50(2)°, 2V(calc.) = 59°, XΛa ≃ 15°, YΛb ≃ 0°, and ZΛc ≃ 38°. There is no evidence for optical absorption, pleochroism or dispersion.

A new X-ray diffraction pattern for the compound cerium oxygen apatite, Ce4.67[SiO4]3O is suggested. The compound was prepared by the solid state reaction of the oxides, CeO2 and SiO2 and has a hexagonal crystal structure with the lattice constants a = 9.6578 Å and c = 7.1187 Å. The sample of the most recent PDF pattern 31-0336* (Visser, 1978) for this compound is believed to be contaminated with significant quantities of N owing to the fact that it was prepared by mixing Ce2O3 and Si3N4 and its very close resemblance to the pattern displayed in the PDF 33-0333 given for the cerium “nitrogen” apatite, Ce5[SiO4]3N.

Diffracted intensities from an X-ray diffractometer operating with fixed or variable divergence slits were compared, following a reported systematic deviation from the theoretical 1/sinθ intensity ratio between these two slit configurations. The theoretical relationship was found to hold over a wide 2θ range provided the anti-scatter slit did not obstruct the beam at higher diffraction angles as the variable slit increased beam divergence. Such obstruction was found to be a possible explanation for the reported deviation.

Cristobalite and tridymite are distinct forms of crystalline silica which, along with quartz, are encountered in industrial operations and industrial products. Because the International Agency for Research on Cancer has designated “crystalline silica” as an IARC Group 2A (probable carcinogen) and quartz and cristobalite as a Group 1 (carcinogen), it is important to properly identify and quantify the silica phase in all materials used in production and encountered in products. Opal is a form of hydrated silica which is also encountered in industry. Although some forms of opal mimic cristobalite and tridymite, they are not truly crystalline. The term “silica” in the industrial sense is used to mean any material whose composition is SiO2 whether it is crystalline or noncrystalline. Some people also consider silica to include hydrated SiO2. There are many forms of SiO2 which have both long-range and short-range order and are recognized as crystalline phases among which are quartz, cristobalite, and tridymite. The hydrated silicas, on the other hand, pose an enigma. Only a few forms show sufficient long-range and short-range order to be considered crystalline. The mineral silhydrite is an example. Opal in all its forms lacks sufficient order to be considered crystalline. Even opal-C, which produces a X-ray pattern similar to the diffraction pattern of cristobalite, lacks not only sufficient order to be considered crystalline but also contains water in the structural make-up. This paper discusses a classification and nomenclature for these forms which is critical to proper regulation. It also reviews the recent literature on tridymite, cristobalite, and opal, and provides an extensive bibliography. Modern studies have shown that opal-A is disordered, but opal-CT and opal-C contain ordered domains that mimic stacked sequences of cristobalite and tridymite sheets such that X-ray patterns show features similar to the crystalline cristobalite and tridymite. There is debate on whether the ordered regions have lost the water that characterizes the opals. In fact, heating studies have shown that all opals show changes on heating characteristic of materials that lose water in the process. The TEM evidence showing domains in the range 10–30 nm in a matrix of disordered opal suggest that the proper term for this system is paracrystalline analogous to inorganic and organic polymers.

A new and improved sample holder suited for small samples has been developed for X-ray diffractometry. This holder is made from a commercial semiconductor grade of silicon wafer grown and cut along the [100]-axis, i.e., Si(100). This new holder not only meets almost all basic requirements of an ideal holder, namely, flat and damage free surface, low background noise, few interference peaks, and desired shape with different cavity sizes, but also provides additional advantages for measuring crystallite sizes and mass absorption coefficients. Furthermore, this holder is easy to clean and has good appearance because of its polished surface. A U.S. patent has been issued and a commercialization effort is underway.

Two new thiophosphates with an original structure corresponding to formula ATi2(PS4)3 (with A=Na,Ag) were synthesized by solid-state reaction. The two compounds are isostructural, hexagonal space group P6cc, Z=8. A single crystal of NaTi2(PS4)3 has been studied. Unit-cell parameters were determined for NaTi2(PS4)3 and AgTi2(PS4)3, respectively: a= 19.9131(6) Å, c= 11.5542(7) Å, V=3967.8(3) Å3 and a=20.0146(8) Å, c= 11.5467(8) Å, V=4005.7(4) Å3. Powder diffraction data are reported.

X-ray powder diffraction data are reported for the monohydrated ammonium dioxalatotitanyl (IV). The crystal system is monoclinic with space group P21/c. Refined unitcell parameters are a = 13.484(3), b = 11.325(2), c = 17.673(3) Å, and β = 126.613(8)°.

The multicomponent Rietveld profile refinement technique for powder neutron diffraction patterns has been applied to arrive at a quantitative phase analysis of crystalline Ce2Fe17 and α-Fe impurity in a powder specimen of Ce2Fe17.

X-ray powder-diffraction data for Pb2(C2O4)(NO3)2·2H2O were obtained. The crystal system was determined to be monoclinic. The unit-cell parameters were refined to a=10.613(2) Å, b=7.947(2) Å, c=6.189(1) Å, and β=104.48(2)°.

Three new compounds of generalised formula [Cu(LIII)XY]·nH2O [LIII=pymep, terpy; X=I, N3; Y=I, NO3, PF6; n=0,1], pymep (C14H15N3)=N-(6methyl–2-pyridyl–methylene) -2-(2-pyridyl)-ethylamine and terpy (C15H11N3)=2,2′;6′,2″-terpyridine have been prepared by reaction in solution. Crystal data were determined by single-crystal methods. Powder diffraction data and densities determined by a flotation method are also presented.

An X-ray analysis method has been developed for the quantitative analysis of pyrite (FeS2) in coals and lignites. Requiring neither the use of external or internal references, the method linearly relates diffraction peak area in the absorption corrected X-ray diffractogram obtained from the finely powdered coal to the pyrite abundance. The [311] diffraction peak of pyrite (FeS2) has been used to develop the analysis protocol. The Argonne premium coals have been used as the experimental subjects. The abundance of pyrite in each coal has been measured from the absorption corrected diffractograms, which has been constructed from the experimentally measured diffraction intensities and the mass absorption coefficient of each coal sample. The accuracy (accessed from the figure-of-merit and the net count uncertainty associated with the 1.63 Å pyrite peak) as well as the lower limit of detection for pyrite in these coals is presented. The role of the mass absorption coefficient in the conversion of the measured intensity to the absorption corrected intensity is discussed.