An X-ray detector chain consisting of a Xe-filled proportional detector followed by a pulse height analyzer tuned to 8.1 keV may register energies between 5 and 45 keV, although with a low efficiency at the edges. For diffraction experiments on single-crystalline substrates, these diffracted intensities can be significant. In the high-energy range, regions of even higher intensity are found due to the so-called escape process. In the diffraction angle scan of an (001) oriented Si single-crystal measured with a low (fixed) incidence angle, we have identified 21 peaks, originating from three different diffraction processes: diffraction from white radiation, diffraction observed via an escape process, and crystal truncation rod scattering. These peaks interfere with diffraction studies if such a single crystal is used as a substrate for polycrystalline samples. A great reduction in the substrate background and removal of most of the substrate diffraction peaks is achieved with a graphite monochromator or with a graphite monochromator together with a β-filter.

X-ray powder diffraction data are reported for a series of isomorphous compounds of [Ln2(CrO4)3(H2O)5]·2H2O, where Ln=La, Pr, Nd, Sm, or Eu. The compounds crystallize in monoclinic space group P21/c (No: 14) with Z=4. Refined unit cell parameters and indexed powder diffraction patterns are given.

The utility of ultra-high-temperature (2100 °C) X-ray powder diffraction technique for investigating the high-temperature phase relationships of two pseudobinary mixtures, Al2O3/Y2O3 and AlN/SiO2, is described. The in situ analysis to 1600 °C was carried out using a platinum holder and a Pt/Rh thermocouple; whereas analysis beyond 1600 °C was performed with a tungsten holder, extremely pure, oxygen-free inert gas environment, and an opticalpyrometer to monitor temperatures up to 2100 °C. The solid-state interaction between Al2O3 and Y2O3 commenced with the formation of Al2Y4O9 (YAM), a yttria rich compound, at 1300 °C followed by AlYO3 (YAP) and Al5Y3O12 (YAG) at 1400 °C. Further heating to 1500 °C and above resulted in the increased concentration of YAG at the expense of the other two phases, followed by melting of the entire sample at 2050 °C. The only phase formed during cooling (from the molten state) was YAG. AlN and SiO2 did not react with each other, in an inert atmosphere, and they remained as separate, discrete phases even at 1600 °C. In the presence of oxygen, they reacted to form mullite and cristobalite, or SIALON depending on the partial pressure of oxygen.

Considering the thermal expansion of silicon at ambient conditions, the lattice parameter will change 0.00032 Å for a 10 °C range. This range is measurable with modern diffraction instrumentation illustrating the importance of knowing the accurate lattice parameter, the temperature of measurement, and the thermal expansion coefficient. The best value for the expansion coefficient is 2.45×10−6/°C.

Numerous spurious X-ray peaks were encountered during grazing incidence angle diffractometer scans of ceramic and polymeric thin films on crystalline and amorphous substrate materials. At least three possible sources of spurious peaks are identified. (1) At (2θ) values greater than ∼ 10°, Laue reflections from characteristic and Bremsstrahlung continuum radiation produce spurious peaks with a (2θ) dependence on X-ray incident angle and sample orientation. At (2θ) values less than 10°, (2) specular X-ray reflection from a boundary between two media of different indices of refraction and (3) diffuse surface scattering produces spurious peaks with a dependence on X-ray incident angle and sample surface topography. From an understanding of the spurious peaks, improved experimental techniques may be developed. Because these peaks can interfere significantly with grazing incidence diffractometer scans, it is particularly important to those making studies of thin films by this asymmetric diffraction geometry to be aware of the existence and origins of these spurious peaks.

The new compound, KCr3(SO4)2(OH)6, was prepared by low-hydrothermal synthesis. The structure was refined by the Rietveld technique in space group (Z = 3), a =7.2416(3) Å, c = 17.0788(9) Å, V = 775.63 Å3, Rp = 7.7, Rwp =10.1, RB = 6.8. The compound is isotypic with alunite, KAl3(SO4)2(OH)6. The temperature of decomposition under nitrogen atmosphere to a hitherto unknown form is about 550 K. The water content of alunite-type compounds is discussed.

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.

An increasingly frequent used sample holder, the zero-background holder (ZBH), is evaluated for use in external standard calibration of powder patterns. The effectiveness of the ZBH calibration method is determined by comparison to the conventional internal- and external-standard calibration techniques. The three calibration methods are compared using the results of lattice parameter refinements of test powders, using Si as the standard. Several test materials were used in the evaluation which cover a wide range of absorption coefficients so sample transparency effects can be distinguished from sample displacement effects. Results of the calibrations clearly indicate that the ZBH method gives precision and accuracy comparable to the internal-standard method, and significantly better than the external-standard technique. In addition, the ZBH method yields substantially better results than the internal-standard method for materials with low absorption coefficients. Low-angle calibrations are also made on a ZBH using a proposed standard, silver behenate, which has peaks from 1.5° to 20° 2θ. These calibrations have shown that if care is not taken to establish a monolayer of powder on the ZBH crystal, significant errors in refined lattice parameters will result.

Recent X-ray single-crystal diffraction studies have shown that CuFeSe2 crystallizes in the tetragonal system with space group P2c [, No. 112], Z = 4, with a =5.530(1) Å and c = 11.049(2) Å, c/a = 1.998. This material had been reported as pseudocubic with a =5.53 Å. The purpose of this paper is to present new X-ray powder diffraction data for CuFeSe2 and to compare the results with those reported for eskebornite, a mineral with ideal chemical composition CuFeSe2, and with those obtained from single-crystal structure data.

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.

The accuracy of the unit-cell parameters refined by using the whole-powder-pattern decomposition method is discussed. Powders of W, ZnO, TiO2, BaTiO3 Mg2SiO4, Al2SiO5 (+α-SiO2), and monoclinic ZrO2 were used as test samples. Two internal standard reference materials of Si and CeO2 and two types of powder diffractometers were used for data collections. The systematic peak-shift was corrected by determining the unit-cell parameters and the error function simultaneously during the whole-pattern-fitting. The estimated standard deviations for sample means ranged from <10 ppm (10−6) in cubic symmetry to 20∼50 ppm in monoclinic symmetry. These analyses could be carried out almost automatically in a computation time of less than l min for each sample on a workstation. The use of symmetric experimental profiles, obtained by the suppression of axial divergence, is very effective and of essential importance for improving the accuracy of unit-cell parameters.

A simple procedure was devised for the preparation of a standard KCl powder to be used for the experimental determination of the instrumental profile in the Bragg–Brentano geometry. The standard was tested on several diffractometers, and narrow Bragg reflections in the range 28°–132° were recorded adopting various experimental conditions. Profiles were modeled with analytical functions, to describe the trend of width and shape of the instrumental profile as a function of the diffraction angle. Some indications were given to perform reliable profile fitting and line broadening analysis; a high resolution setup, obtained by employing narrow slits, large goniometer radius, and a monochromator in the diffracted beam, gives narrow reflections, even though the intensity of the diffracted beam is considerably reduced. The choice of these experimental conditions, which can be achieved using the majority of the commercial instruments, leads to symmetrical profiles, even at relatively low angle (2Θ=28°), which are highly recommended for reliable profile fitting and line broadening analysis.

Literature data pertaining to the crystal chemistry, crystallography, and X-ray powder-diffraction properties of phases reported in the system BaO-CuOx are compiled. Reported phases include BaCuO2−2.12, BaCuO2.26−2.39, BaCuO2.5, Ba2CuO3+x, Ba2Cu3O5+x, BaCu2O2+x, Ba3Cu5O8, Ba3CuO4, BaCu3O4, Ba3Cu2O4+x, Ba5Cu3O6+x, and BaCu2O3. The existence of some of these phases, however, still has to be verified. Most of these compounds are nonstoichiometric in oxygen. Their oxygen content, and in some cases even their crystal structures, vary with oxygen partial pressure. There are also reported indications that the cations Ba and Cu are not stoichiometric in the cubic BaCuO2-type compounds.

Ba0.5+x/2Zr2P3−xSixO12 or BaZPS compounds were synthesized by the sintering of powders formed by a solid-state reaction. The cell parameters of Ba0.5Zr2P3O12 and Ba0.5875Zr2P2.825Si0.175O12 were determined from X-ray diffraction (XRD) data based on the (#148) space group with hexagonal setting. The cell parameters were found to increase with increasing Si content in BaZPS.

X-ray powder diffraction data for Ti2O2(C2O4)(OH)2·H2O were obtained. The crystal system was determined to be orthorhombic with space group C2221. The unit cell parameters were refined to a = 1.0503(2) nm, b = 1.5509(3) nm, and c = 0.9700(1) nm.

The X-ray powder diffraction pattern of hydrated lithium monoborate LiB(OH)4, sometimes formulated LiBO2·2H2O, has been obtained. Refinements of indexed reflections yielded the following parameters: a = 9.1732(7)Å, b = 7.9622(6)Å, c = 8.5354(8)Å, space group Pbca, Z = 8, Dx = 1.827, Dm = 1.83 g/cm3. The Smith–Snyder figure-of-merit is F30 = 101(0.007,44).

Single crystals and powder samples of Ba4ZnTi11O27 and Ba2ZnTi5O13 have been synthesized and studied using single-crystal X-ray precession photographs and X-ray powder diffraction. Unit cell dimensions were calculated from a least-squares refinement with a final maximum Δ2θ of 0.05°. Both phases were found to have monoclinic cells, space group C2/m. The refined lattice parameters for the Ba4ZnTi11O27 compound are a= 19.8687(8) Å, b=11.4674(5) Å, c=9.9184(4) Å, β= 109.223(4)°, and Z=4. The refined lattice parameters for the Ba2ZnTi5O13 compound are a= 15.2822(7) Å, b=3.8977(1) Å, c=9.1398(3) Å, β=98.769(4)°, and Z=2.

Sm(OH)2NO3, was prepared by hydrolysis of the corresponding nitrate, leading to a product which is insoluble in water. IR-spectroscopy showed a comparison with the analogous Gd-compound. The temperature of decomposition to SmONO3 is below 573 K. The structure was refined by the Rietveld technique in space group P21, (Z=2), a=6.3852(3) Å, b=3.7784(2) Å, c=7.7402(3) Å, β=97.572(3)°, V=185.11 Å3, Rp=4.9, Rwp=6.3, RB=4.0. The compound is isotypic with Ln(OH)2NO3 (Ln=Pr,Nd,Gd). Infrared spectra and thermal decomposition data are also given for the Gd phase.

The crystal structure data have been determined by X-ray diffraction for three rare earth magnetic materials, Nd2Co14B, Pr2Co14B, and Pr2Fe14B. The data were evaluated with several computer programs desingned for that purpose. The crystal structure for Nd2Co14B and Pr2Fe14D determined by X-ray diffraction agree with those obtained earlier by neutron diffraction.