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.

Standard Reference Materials (SRM) are stable materials which have one or more properties certified by the National Bureau of Standards. A general introduction is given to the types of SRM's and their certification. SRM's for X-ray diffraction are described in detail, including their intended use and their certified and other properties. New SRM's are under consideration as quantitative standards, intensity and line shape standards, and materials properties standards.

Observed and calculated X-ray powder diffraction data are given for the mineral beryllonite, NaBePO4, from Stoneham, Maine, U.S.A. Diffractometer data taken with CoKα1 radiation and Guinier film data registered with CuKα1 radiation are compared. Two independent procedures were employed to index the patterns.

This paper presents the powder X-ray diffraction data of BaFI recorded using a Guinier diffractometer and Mo Kα1 radiation. BaFI stabilizes at standard temperature of 25 °C and standard-atmospheric pressure (STP) in the tetragonal structure (space group P4/nmm; No. 129) with lattice parameters a=4.660(1) Å and c=7.960(5) Å. Our observed pattern is different from the existing observed powder diffraction data reported in the PDF files 34-716 (Beck, 1976) and 31-139 (), but matches almost perfectly with the pattern calculated by us from the reported single crystal data ( and with the calculated data available in PDF file 70-0481. Further, our data provide a number of new Bragg peaks extending beyond the range of d values available in the existing PDF files.

Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitative information by resolving the overlapping peaks in X-ray powder diffractograms collected from mixtures of kaolinite and ripidolite. A series of diffractograms were collected from known mixtures of the two minerals. The diffractograms were then processed using Fourier self-deconvolution over a selected range between 23 and 27° 2θ (encompassing the overlapping peaks of kaolinite (002) and ripidolite (004) at 24.85 and 25.13° 2θ, respectively). Once deconvoluted, areas under individual peaks of kaolinite and ripidolite were calculated using curve fitting. The calculated percentage of kaolinite in the mixtures was then plotted versus the true weight percent of kaolinite. The same procedure was conducted on the original diffractograms using only curve fitting without first deconvoluting. A comparison of results shows that, provided the number of peaks are known, both methods give nearly equal results. However, Fourier self-deconvolution, by increasing the resolution, greatly improves the ability to detect overlapping peaks.

An X-ray diffraction pattern for ErNi2Ge2 at room temperature is reported. ErNi2Ge2 is tetragonal with lattice parameters a=4.0191(2) Å, c=9.7643(2) Å, space group I4/mmm, and Z=2. The lattice parameters derived from Rietveld analysis agree well with the results of a least-squares refinement.

Tacrine hydrochloride monohydrate, velnacrine maleate and suronacrine maleate have been investigated by means of X-ray powder diffraction. The unit cell dimensions, determined by single-crystal diffraction data, agree well with those of powder diffraction analysis, which is characterized by good figures of merit for the three drugs. Present work assures that single-crystals are good representatives of the commercial powdered samples, since experimental and simulated (from structure determination) powder patterns are practically identical.

Powder X-ray diffraction data for cubic La0.3Sr0.7CoO3−δ, perovskite prepared by a combustion method, using metal-EDTA complexes are reported. The cubic cell parameter is: ac = 3.8323(9)Å.

Limitations in powder diffractometry imposed by scatter slits and/or a diffracted-beam monochromator, which have been ignored in the past, are discussed and mapped quantitatively. These limitations become manifest especially with ωoffsets, i.e.in stress measurements and with ωoscillation to improve the reproducibility of intensities in the presence of too coarse grains. The limitations can only be established with knowledge of slit sizes and with precise alignment of all slits, their holders and the diffracted-beam monochromator. To that end, concise, accurate procedures for obtaining these measurements in-situare proposed.

The Powder Diffraction File (PDF) is a collection of single phase X-ray powder patterns, maintained and distributed by the JCPDS-International Centre for Diffraction Data. Over the past 10 years there has been increasing use of the PDF in computer readable form, but the limited amount of disk space available on most commercial powder diffractometer systems has limited use to a small subset of the total PDF. The recent availability of low-cost Compact Disk Read Only Memory (CD-ROM) systems offers an attractive alternative to conventional disk media. This paper describes a low-cost Personal Computer/CD-ROM system, “PC-PDF”, having a total available storage of 550 Mbytes. While seek times are relatively slow – typically, 0.5 seconds are required to traverse the complete PDF – by use of optimum packing and access algorithms, search strategies based on PDF numbers, chemistry, strongest d-spacing, etc., operate at a speed causing no great inconvenience to the user.

Detailed procedures for solving small crystal structures ab initio with the maximum-entropy (ME) methods using X-ray powder diffraction data are described by determining the structure of the low-pressure phase of magnesium boron nitride, Mg3BN3(L), which was previously solved by one of the authors and co-workers using the Patterson method and the direct methods. The simple ME method devised by Gull, Livesey, and Sivia failed to correctly phase the structure-factor data, leading to noninterpretable electron-density maps. This method, maximizing the entropy under the constraints of the observed structure factors with subsequent incorporation of strong extrapolates in the basis set, trapped the solution in a local entropy maximum, from which there is no way to move. The multisolution method of phase determination by entropy maximization and likelihood evaluation, developed by Bricogne and Gilmore, successfully located all the Mg, B, and N atoms in one cycle of phase extension. The correct solution had a highest log-likelihood gain, but a minimum entropy, among the multisolutions generated by phase permutation.