The synthesis and unit cell refinement of two industrially important ferroelectric compounds with the tungsten-bronze structure are reported.

Twenty-four coal samples representing the four major rank types were analyzed by the X-ray RIM methodology which includes mass absorption analysis by X-ray transmission and quantitative X-ray powder diffraction. Twenty-three separate mineral species were observed in the samples, many of which could be quantified in the whole coal analysis. Several mineral species at levels of 5 weightpercent or less were observed only in the ashed scans. Some dehydration and reconstitution reactions were observed in the ashing process, including the combination of organically bound alkaline-earth elements and sulfur to form bassanite and magnesium sulfates. Quartz and kaolinite dominated the silicate mineral portion of the mineralogy, whereas calcite and siderite represented the carbonate; pyrite with associated sulfate oxidation products were generally present as well. The X-ray transmission studies were successful in estimating the carbonaceous matter in the whole coal samples and comparison of the chemical oxides derived from the X-ray data with direct analyses from the Penn State data sheets revealed good correlations, although significant departures occurred for some species and a systematic underestimation of aluminum oxide from the X-ray clay peaks was observed. This study suggests that the RIM procedure can be applied to coal mineral and amorphous component analysis on a routine basis.

The Semi-manual Structure-sensitive SEARCH-MATCH procedure [Frevel, (1982), Anal. Chem. 54, 691–697] has been automated for the Hewlett-Packard HP 3354 Computer. The software is coded in the interpretive HP LAB BASIC II language. A core file of 1026 selected powder diffraction standards has been compiled covering the common crystalline phases encountered in industry, the ubiquitous crystalline minerals, and prototypes of the more frequently found crystal structures. Solid solutions can be readily identified.

Introduction: Phase transition has been recently observed in Cs2CdI4 (Touchard, Louër, Auffrédic & Louër, 1986). Thermal analysis has shown that the transformation occurs at 122°C. By quenching, the high temperature phase (β) can be stabilized at room temperature. In the present work we report the X-ray diffraction powder data, at room temperature, for the two phases α- and β-Cs2CdI4. Both phases have been indexed automatically by using powder indexing methods.

The variables of reflection overlap, crystallinity and crystallite size, primary extinction, microabsorption, chemical substitutions, preferred orientation, and analytical procedures affect quantitative analysis by powder X-ray diffraction. The intensity of the strongest reflection (I) of 39 minerals from a typical sedimentary environment divided by the intensity of the strongest reflection (Ic) of corundum, I/Ic, may be used to determine mineral percentages. Because of the numerous variables mentioned above, the I/Ic ratios used should be taken from multi-mineral specimens that occur either in the same geological formation for quantitative analysis (±7%) or in a similar geological formation for quantitative analysis (±30%).

An improved method of alignment of a Philips diffractometer equipped with a theta-compensating slit is described. The method employs a special fluorescent screen which is flat to better than 10 microns. The procedure results in accurate alignment of the theta-compensating slit at low angles and assures reliable intensity data down to one degree two theta or less.

The ternary compound YAg0.4Ga1.6 has the CaIn2-type structure. The only variable positional parameter z was determined by graphical methods from visual observations of intensities on a Debye-Scherrer pattern. Cu or Ni substitutions for Ag also result in a ternary CaIn2-type structure.

Twenty seven new rare earth (Ln) compounds CuLn2 Ge2O8, CuLn2Ge4O12 and CuLn2Si4O12 have been synthesized. The powder diagrams were indexed and solid solutions of silicates and germanates were investigated. Structural variations with temperature, lanthanide contraction and Ge/Si substitution are described. Indications for second order phase transitions were found.

A quantitative X-ray diffraction method for the phase analysis of fertilizers of the NPK 12-19-19 type has been worked out together with a complex system of computer software. A bank of synthetic standards was employed in the solution of the problem. To reflect the real structure of the phases determined in fertilizers as against the structure of synthetic standards, intensity coefficients based on chemical analyses were assigned to individual phases in the bank of standards.

μPDSM, a powder diffraction search/match system, is derived from the original interactive time-sharing system written for the NIH/EPA Chemical Information System. Transformed and essentially rewritten, it still searches the entire JCPDS database, but on an inexpensive IBM PC microcomputer. In the transition from mainframe to micro, μPDSM has lost none of its speed or performance. Indeed, the basic discriminating power of the search/match algorithms had to be improved, since the Powder Diffraction File is some 50% larger than it was when The CIS version was in operation. While μPDSM will solve typical problems on a “push-button” mode, it provides an environment that promotes optimization of search parameters by the diffractionist, and provides all of the subfile and chemistry functions associated with larger systems.

The indexed X-ray diffraction powder data of sodium triaqua-hexa-(nicotinato-tri-μ-oxo-tri-chromium(III) perchlorate) hexahydrate {Na [Cr3 O(C6H5NO2)6(H2 O)3] [ClO4]8·C6H5NO2·6H2O, NICCR} is reported. NICCR crystallizes in the hexagonal space group P63/m. The refined cell parameters were determined by employing a Siemens Debye-Scherrer camera (Fe Kā radiation, λmean= 1.93736 Å). The cell constants are a = 13.573(2), c = 24.901(5) Å, V = 3972.8 Å3 and Dx =1.68 Mg m-3 (Dm =1.67 Mg m-3). The quantitative figure of merit (FN) for NICCR is F27 = 32(0.010,81). The JCPDS Diffraction File No. is 36–1978.

Florencite-(Nd) [(Nd,Ce)Al3(PO4)2(OH)6], was first described by Milton and Bastron (1971) from fracture surfaces in weathered cherts of the Franciscan Complex, south of Sausalito in Marin County, California. Florencite-(Nd) occurred there as a moderate-brown pulverulent earthy material; individual crystals were not discernible under microscopic examination. A semi-quantitative spectrographic analysis showed the presence of Nd (3 wt. %) and Ce (0.5 wt. %). No powder data for florencite-(Nd) exists in the current powder diffraction file.

Ternary systems CuO-M2O3-TO2 with T = Si, Ge and M3+ = Al, Ga, Fe, Cr, Bi and Y were investigated at 1000°C. Ternary compounds were found only for M3+ = Y. CuY2Ge2O8 is monoclinic with a = 9.477 Å, b = 15.005 Å, c = 8.030 Å and β = 147.50°; CuY2 Si4 O12 is monoclinic with a = 7.052 Å, b = 14.283 Å, c = 4.738 Å and β = 103.32°; CuY2Ge4O12 is triclinic with a = 7.185 Å, b = 7.949 Å, c = 4.910 Å, α = 86.83°, β = 102.70° and γ = 113.84°. The last two structures are closely related. The binary double oxide series Cu2Ln2O5 was reinvestigated.

The neodymium hydroxynitrate, Nd(OH)2(NO3).H2O, (PDF #37-1841) has been investigated by means of X-ray powder diffraction data. The unit cell dimensions were determined from diffractometer methods, using strictly monochromatized CuKα1 radiation, and evaluated by indexing programs. The monoclinic cell found was a = 19.381(4)Å, b = 3.884(1)Å, c = 6.291(1)Å, β = 96.43(2)°.

Complete X-ray powder data is recorded from type specimens of the minerals nissonite and waylandite. Debye-Scherrer films of 114.59 mm diameter were measured with an automated densitometer. A wide step width of 0.08°2θ was required, because the average reflection width at half height was 0.5°2θ. The 2θ positions and relative intensities of the reflections were calculated from a negative second derivative function based upon a five point curve.

Patterns useful for identification are obtained by automated diffractometer methods. The lattice constants from the experimental work are refined by least-squares methods; reflections are assigned hkℓ indices consistent with space group extinctions. Relative intensities, calculated densities, literature references, and other relevant data are included.

Features of the powder diffraction patterns of known polytype-like modifications of Ca3GeO5, such as 2H, 9R and 24R types, and a monoclinic polymorph have been studied by means of the patterns calculated based on their crystal structures. The result has provided keys to identify them when they coexist in the same synthetic product. Accounts have been given on the crystallographic features of the building layer and rules for layer stackings of the modifications in general. Any modification may then be constructed to predict its powder diffraction pattern.

The aim of any diffraction experiment is to obtain reproducible data of high accuracy and precision so that the data can be correctly interpreted and analyzed. Various methods of sample preparation have been devised so that reproducibility, precision and accuracy can be obtained. The success of a diffraction experiment will often depend on the correct choice of preparation method for the sample being analyzed and for the instrument being used in the analysis.

A diffraction pattern contains three types of useful information: the positions of the diffraction maxima, the peak intensities, and the intensity distribution as a function of diffraction angle. This information can be used to identify and quantify the contents of the sample, as well as to calculate the material's crystallite size and distribution, crystallinity, and stress and strain. The ideal preparation for a given experiment depends largely on information desired.

The following new or updated patterns are submitted by the JCPDS Research Associateship at the National Bureau of Standards. The patterns are a continuation of the series of standard X-ray diffraction powder patterns published previously in the NBS Circular 539, the NBS Monograph 25, and in this journal. The methods of producing these reference patterns are described in this journal, Vol. 1, No. 1, p. 40 (1986).

The data for each phase apply to the specific sample described. A sample was mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2-theta values for these standards are specified in the methods described (ibid.). Data, from which the reported 2-theta values were determined, were measured with a computer controlled diffractometer. Computer programs were used to locate peak positions and calibrate the patterns as well as to perform variable indexing and least squares cell refinement. A check on the overall internal consistency of the data was also provided by a computer program.

The following new or updated patterns are submitted by the JCPDS Research Associateship at the National Bureau of Standards. The patterns are a continuation of the series of standard X-ray diffraction powder patterns published previously in the NBS Circular 539, the NBS Monograph 25, and in this journal. The methods of producing these reference patterns are described in this journal, Vol. 1, No. 1, p. 40 (1986).

The data for each phase apply to the specific sample described. A sample was mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2-theta values for these standards are specified in the methods described (ibid.). Data, from which the reported 2-theta values were determined, were measured with a computer controlled diffractometer. Computer programs were used to locate peak positions and calibrate the patterns as well as to perform variable indexing and least squares cell refinement.