Highly uniform fine powder sample layers may be prepared for X-ray diffractometry by aerosol suspension and collection on glass fiber filter substrates. A tubular aerosol suspension chamber (TASC) has been fabricated for this purpose. Essential components include a 500 ml gas buret, 4.7-cm filter cassette, rotameter, and rotary pump. Aerosol particles are generated within the TASC buret by convection within a fluidized bed of glass beads mixed with the sample. Exceptional uniformity of load and randomness of particle orientation has been demonstrated for samples prepared with this system. For quantitative analytical work accurate intensities may be obtained using corrections to raw intensities based on fundamental sample and filter properties.

The crystal structure of metastable Li2Si2O5, Fw = 150.05, has been refined by the Rietveld method using high resolution X-ray powder diffraction data recorded at the Daresbury Synchrotron Radiation Source on the new 8.3 diffractometer. Li2Si2O5, in keeping with many compounds of interest to the materials scientist, exhibits relatively broad diffraction peaks. It is important to establish the quality of crystal structure data that may be obtained from such materials on this new instrument. Various functions were used to model the peak shape from this instrument; a split-Pearson VII function appeared to be marginally superior to Pearson VII or Pseudo-Voigt functions. Refinement was carried out using the split-Pearson VII in the space group Pbcn (60) and terminated with a = 5.6871(6), b = 4.7846(5), c = 14.645(1) Å, V = 398.50 Å3, Z=4, Dc= 2.502 gcm−3, Rwp = 17.06, Rex = 14.48 and Χ2 = 1.39. The refined parameters are compared with those obtained from a previous single crystal X-ray determination.

X-ray powder data originally published for innelite—Na2Ba3(Ba, K, Mn)(Ca, Na)Ti(TiO2)2[Si2O7]2(SO4)2—were erroneously those of catapleiite. The new data reported here are compared with powder data calculated from the published structure. The cell is triclinic (space group P1, Z=1), a=14.71(1) Å, b=7.115(7) Å, c=5.379(4) Å, α=90.02(7)°, β=94.68(8)°, γ=98.43(9)°, V=555.0(6) Å3, F30=5.2(0.053,109).

An algorithm has been derived, forming the basis of a computer program called BBCCURV, which calculates a Bragg-Brentano X-ray diffractometer intensity correction curve (intensity correction factor Kivs. 2θi) given the diffractometer and sample dimensions, and the effective (not theoretical) linear absorption coefficient of the sample. Use of this calibration curve gives a set of intensity data free from aberrations, which are caused mainly by sample transparency, curvature of the diffraction cones passing through the receiving slit and possible beam overflow past the specimen at low angles.

The algorithm was confirmed with a full-profile Rietveld refinement of Bragg-Brentano X-ray diffraction data from a H+-ZSM5 zeolite sample. On introducing a BBCCURV correction curve, the profile R-factor over the pattern points dropped from 30.8% to 16.5%, a significantly better fit when the data were corrected with a BBCCURV curve.

BBCCURV intensity calibration curves from LiF (μ= 1.5 mm−1) through zeolites, clays, ZnO, rutile, Pb(NO3)2and finally solid metal (μ= 1000 mm−1) (CoKα) indicate upward revision of the measured diffractometer intensities by factors of between 2 and 10 at 2θ= 5° for these sample types, normalised to a correction factor of 1.0 at 2θ= 44°. Corrections of this magnitude to Bragg-Brentano data are thus significant in full-profile structure refinement and quantitative analysis with Bragg-Brentano data. Use of a variable divergence slit (VDS) is not appropriate in full-profile refinements as the intensity aberrations are magnified, and conversion from VDS data to aberration-free data is sample- and transparency-dependent, and not the simple area (sinθ)−1function generally assumed. Use of a fixed divergence slit with a BBCCURV-type calibration is recommended.

Results are given of an assessment of a Rietveld-type X-ray powder diffraction pattern fitting structure refinement technique for assaying powdered mixtures as an alternative to conventional discrete peak empirical methods of the type described by Klug and Alexander (1974) and Chung (1974). The values obtained for a mixture of corundum and α-quartz, following calibration of the instrument with a profile of the former, indicate that this technique has excellent potential as an analytical tool.

The anhydrous and hydrated lithium monoborates have been studied. The most hydrated phase is LiBO2·8H2O; its structural formula in the P3 space group is Li(H2O)4B(OH)4·2H2O. Refinement of the cell parameters yielded the following results: a=6.5483(5) Å, c=6.1692(7) Å with F(30)=64(0.015, 32), Z=1, and Dx=1.402 g/cm3. This phase gives LiB(OH)4 by spontaneous dehydration. An X-ray powder diffraction study of LiB(OH)4 as a function of temperature indicated three poorly crystallized hydrates. Two of these hydrates have the formula LiBO2·0.3H2O; the other, LiBO2·xH2O, has an undetermined water content. Crystal data for α-LiBO2 have been obtained: a=5.8473(10) Å, b=4.3513(6) Å, c=6.4557(10) Å, β=115.08(1)°, F(27)=58.5(0.001, 41); space group P21/c, Z=4, and Dx=2.18 g/cm3. β-LiBO2 does not exist but corresponds to the α-LiBO2 form observed at 600 °C. Numerous other LiBO2 forms reported recently have not been found.

The Debye-Scherrer technique and filtered Cu Kα, radiation were used to obtain powder data for reflections to an angle of 2θ = 155°; a vertical scanning diffractometer was used to obtain intensity data to an angle of 2θ = 99°. The space group is with Z = 4. The lattice parameters of the tetragonal unit cell were measured to be a = 6.189 (1) Å and c = 12.391 (1) Å with c/a = 2.002 The unit cell volume was calculated as U = 474.6 (2) Å3 and the X-ray density as Dx = 6.07 ± 0.003 gm cm−3. By comparing measured and theoretical intensity values, the sublattice distortion parameter x was estimated to be x = 0.227 (12).

Crystal structure analyses by the Rietveld method have shown that the framework structures of zeolites ZSM-5 and ZSM-8 are essentially identical. Therefore, it is difficult to distinguish the two phases especially when the template-free H forms are studied. In addition, some inconsistencies in publications on the two zeolites aggravate the correct interpretation of the powder diagrams. A powder pattern published for ZSM-8 which indicates significant differences between the lattice constants of ZSM-8 and ZSM-5 is shown to be incorrectly indexed. Correct reindexing gives lattice constants for ZSM-8 matching average ZSM-5 values. Peak splitting of a ZSM-8 reflection at 2θ≈23° (CuKα) has been used frequently to distinguish ZSM-8 from ZSM-5. However, it is also a common feature of ZSM-5 diagrams when the difference between a and b lattice constants is big enough to separate hkl and khl reflections within the instrumental resolution. Our data on two ZSM-8 samples indicate that cell dimensions of ZSM-8 do not deviate from average ZSM-5 values. It is suspected that effects in the decomposition of crystals upon calcination, and/or morphology and shape of twin individuals, and/or stacking faults account for different sorption properties of the two zeolites rather than differences in their average crystal structures.

Residual strains and microstresses are evaluated for both phase of a hot-pressed, fine-grained α-alumina reinforced with 25 wt% (29 vol%) single-crystal silicon carbide whiskers at temperatures from 25 to 1000 °C. The sample was maintained in a nonoxidizing environment while measurements of the interplaner spacing of alumina (146) and SiC (511 + 333) were made using X-ray diffraction methods. The residual strains were profiled at temperature increments of 250 °C from which the corresponding microstresses were calculated. Linear extrapolation of the SiC ε33 profile indicates that the strains are completely relaxed at a temperature of approximately 1470 °C. These residual stress relaxation results suggest that elevated temperature toughness and fracture strength of this composite may result from cooperative mechanisms.

Music, medicine, escape: Austria, Italy, America. As a very young man, Sigmund Weissmann, before he was 18, had seen the prosperous stability and direction of his youth disintegrate, had, through fortunate foresight and mature determination escaped potential disaster, and had found himself, essentially alone, in New York City. That was April 1939. Within 5 years, his early studies completed and military service over, his future had been established with crystallography, and even more particularly, that aspect of it which was related to the “pathology” of metals. He was to establish one of the first laboratories devoted to research of lattice defects and to lay the groundwork for what is now known as Materials Science. Contemporaneous with the operation of this laboratory and as an outgrowth of his own basic connection with the famous “Brooklyn Poly,” Weissmann included, among his manifold teaching, research, and consulting activities, the acceptance of a position as an editor of the Powder Diffraction File, the PDF. The PDF was then just large enough, just important enough and had just that suggestion of an important reach into the future to necessitate an equally important attention from a group of persons schooled and skilled in the most recent techniques of X-ray powder diffraction. Weissmann (metals), Ben Post (organics), of the Brooklyn Polytechnic Institute and J. V. Smith (minerals) (University of Chicago) were the first thus crystographically trained persons to oversee the PDF.

50-50 atomic percent lead telluride (Altaite), grown by the vapor transport method, was examined with a well aligned Rigaku horizontal beam diffractometer. PbTe is cubic (precise lattice parameter ao = 6.4591(5)Å) with an space group and a calculated density of 8.253 g/cm3. Fully indexed powder diffraction data are presented.

Barium titanyl oxalate tetrahydrate, Ba(TiO)(C2O4)2.4H2O, has been investigated by means of X-ray powder diffraction. Precise powder diffraction data were obtained by a conventional diffractometer with strictly monochromatic radiation. Unit cell dimensions were determined by an indexing program based on the variation of parameters by successive dichotomies. A monoclinic cell was found, a=14.044(2)Å, b=13.812(2)Å, c=13.382(2)Å, β=91.48(1); V=2594.9Å3, which is characterized by the figures of merit M20=46.5 and F30=107(0.0056, 50). The complete powder pattern was reviewed by means of the program NBS*AIDS83 and the 81 first lines were indexed. Structural imperfections were not detected from the diffraction line widths, which are comparable to the instrumental resolution.

A conventional semi-automated powder X-ray diffractometer that was previously equipped with a strip chart recorder for data acquisition has been interfaced to an HP 1000 minicomputer via an analog-to-digital converter. Data acquisition and analysis is now accomplished using CALS chromatographic software and two in-house-developed FORTRAN 77 computer programs. This has resulted in significant improvements in experimental repeatability and accuracy, decreased sample turn-around times, and rapid and facile analysis, manipulation, and comparison of crystallographic data.

Afghanite is a feldspathoid of the cancrinite-group: It is hexagonal, space group P63mc. The afghanite sample was found in the M. Somma-Vesuvio volcanic complex (Italy) and was previously described as davyne: Calculated cell parameters are a = 12.7997(4) Å, c = 21.4062(11) Å; the volume is 3037.2(2) Å3. The strongest lines are: 3.694(100), 3.647(56), 4.826(30), 2.678(25), 2.134(18), 3.999(12), 2.750(12), and 2.771(10). The new data provide quantitative measurement of intensities, an increased number of indexed peaks, and a different empirical formula with respect to the PDF 20-1086.