The Guinier Camera

For the Guinier-camera a compromise between external and internal standard is possible, as the camera allows the simultaneous recording of several samples onto the same film by dividing the camera by the installation of separating disks. Mostly three individual patterns are taken simultaneously pure sample, mixture sample/standard, and pure standard. If one wants to dispense with the mixture, it will be sufficient to put the sample pattern in the centre and a standard pattern at each side of the Guinier-film. 

The Guinier camera (e.g. [1]) is altogether more sophisticated than the pinhole and filtration techniques used in Debye-Scherrer type cameras, and will enable the user to make accurate determinations of lattice spacings up to 15 nm with exposure times of the order of a few tens of minutes for an average sample on a standard X-ray generator. 

Figure 8. The Guinier camera. Sharp monochromatic Bragg peaks are brought to a focus on a cylindrically curved film strip.

Recently, a detailed study4,5 of AB02 compounds confirms that AgFe02 has the CuFe02 (delafossite) structure. The cell dimensions, determined with a Guinier camera, are found to be a = 3.0391 2 A. and c = 18.590 2 A. Single crystals are used to measure resistivity as a function of temperature.6 Silver fer-rate(III) exhibits semiconductor behavior with an activation energy of 0.7 e.V. An unusual anisotropy in resistivity is found withp(j c) = 3 X 107 S2-cm. and P( c) = 2 X 1010 J2-cm. 

It will be assumed here that the X-ray diffraction data were collected on flat films with a point focus camera. This simplifies the theoretical presentation. The TMV data analyzed in the results section were collected on cylindrical films with Guinier cameras, but positions on the cylindrical films can be mapped onto positions on a flat film by a simple geometric transformation. In general, the form of the optical density, D(r,), in a fiber diffraction pattern can be expressed in film coordinates as the sum of contributions from all reflections, I (r,iJ> ), plus a background term, B(r,) ... 

Figure 2 shows the results of the non-linear fitting procedure on a part of the equator, first and second layer lines of TMV. The diffraction pattern used was taken by Dr. S. Warren and Dr. G. Stubbs at the Max-Plank-Institut in Heidelberg, Germany. This pattern was taken on a Guinier camera and the arcsdue to disorientation are not circular. The natural coordinate system (3)of the camera (rather than polar coordi-nates)was used in the deconvolution procedure. The standard... 

Samples of purified EuC12 were analysed for europium and chlorine by conventional analytical methods. Calc for EuC12 Eu, 68.18%. Found Eu, 68.1 x +0.2i Cl, 31.80+0.02. X-Ray diffraction patterns of the polycrystalline samples and residues from the vaporization experiments, to which an internal Pt standard (a = 3.9238 +0.0003 A) had been added, were obtained with a Haegg-type Guinier camera and Cu Ka radiation. The lattice parameters and intensities of the diffraction lines were in agreement with those reported (1) for orthorhombic EuC12 (PbCl2 structure). 

Formation of Pd-Ag alloy (Cat. C) and the presence of PdCx phase after poisoning were analyzed by X-ray diffraction. CuKa X-ray powder diffractograms were recorded with a Guinier camera equipped with curved quartz monocromator. 

On the debit side, the Seemann-Bohlin camera has the disadvantage that the lines registered on the film cover only a limited range of 26 values, particularly on the low-angle side. The Seemann-Bohlin camera, in itself, is now virtually obsolete (the diffractometer has greater resolution), except in combination with a monochromator. The combination is then called a Guinier camera (Sec. 6-14). 

The combination of a focusing monochromator and a focusing camera is known as a Guinier camera, pioneered by Guinier in the late 1930s. Later investigators produced... 

Compared to a Debye-Scherrer camera of the same size, operated directly from the x-ray tube, a Guinier camera provides a much clearer pattern with twice the resolution and about the same exposure time, but any one Guinier camera covers only a limited range of 10. It is best suited to the examination of particular parts of complex patterns. 

The pattern may be recorded with a Debye-Scherrer camera, Guinier camera, or diffractometer. Here again, line intensities depend on the apparatus. In particular, absorption effects cause high-angle lines on a Debye-Scherrer pattern to be stronger, relative to low-angle lines, than on a diffractometer recording, as shown m Sec. 4-10. 

STA 94] STAHL K., The Huber G670 imaging-plate Guinier camera tested on beamline 1711 at the MAX It synchrotron , J. Appl. Cryst, vol. 33, p. 394-396,2000. 

The catalysts were prepared by impregnating Ca(OH)2 with aqueous solution of NaOH applying the incipient wetness method. After impregnation the samples were dried and calcined in CO2 free air at 973 K. Other alkaline earth oxides (Analar) were also used for activity measurements. X-ray diffraction studies were carried out in a Phillips instrument using a Guinier camera applying crystal reflected monochromatic CuK a radiation. IR spectra were recorded by a Perkin-Elmer FTIR 1710 spectrometer. The samples were dried for 1 Oh at 383 K prior to preparing the pellets. The catalytic experiments were carried out in a quartz made reactor, details of the reactor operation and product analysis have been described elswhere [8]. 

In the context of oscillation camera data processing for the monochromator at 1.5 A with a demagnification of 10-30 the system would be far from the Guinier setting the exact (dX/X) (equation 5.9)) would depend on the length of the crystal monochromator illuminated (see section 6.1). 

Samples of the reaction mixtures were taken after 3 hrs, 18 hrs, 112 hrs, and 14 days. The solid products were filtered off and washed thoroughly with distilled water. The dried solids were all examined under the microscope and identified by means of x-ray powder patterns using a Guinier camera. Selected samples were characterized further by means of chemical analyses, density and sorption measurements, electron microscopy, and thermal analyses (DTA and TGA). 

N2 make up gas flow of 20 ml/min before the reactor. N2 and O2 flows were controlled by mass flow controllers. The contact time was varied between 0.3-0.03 s corresponding to gas flows of 100-1000 ml/min at a catalyst volume of 0.5 ml. A nondispersive IR analyser was used for CO and CO2 and an FID for hydrocarbon analysis. All relevant signals were collected by on line computer. The amount of CO2 formed was taken as a measure of the catalytic activity. XRD using a Philips machine equipped with Guinier camera and KRATOS XSAM XPS machine were applied for characterizing the catalyst before and after the catalytic test. 

X-ray diffractometry, T =300K. The lattice parameters and some bond lengths of the three different kinds of samples discussed in sect. 3.1.2 have been measured with X-ray diffraction using either a Guinier camera with internal standard (Rusiecki et al. 1990, Rusiecki and Kaldis 1991, Conder et al. 1994a) or a STOE powder diffractometer... 

Tables 5, 6 and 7 give the values of the XRD lattice parameters at r=300K (Guinier camera, with Si standard) for the CAR, BAO and DO samples, respectively. To confirm the anomalies in the lattice parameters found by XRD, an NPD refinement was performed as a function of temperature at 12 oxygen contents. Tables 8a-d give neutron diffiaction data of 12 selected BAO-sample compositions at T=5 K and 300K (Hewat et al. 1991). Figure 29f shows the c-parameter vs. x as measured at 5 K. Both anomalies found with XRD were confirmed, as apparent upon comparison with fig. 28a. The same is true for the i-parameter shown in fig. 29g, where the decrease in the overdoped range is seen more clearly than in fig. 29d. The NPD bond lengths of the BAO samples are discussed in more detail in conjunction with the dimpling transition corresponding to the minimum of the c-axis (sect. 6.1).

A quartz crystal can be polished and elastically bent to a radius in the range 200-400 mm, with the crystal being 2 mm thick. The actual value of R must be chosen to suit the wavelength range of interest and the size of the camera. The configuration of a Guinier camera is illustrated in Fig. 8. The sample is interposed in the beam some distance before its focal point, so that a reasonable volume can be irradiated. The diffraction pattern then falls on a circle whose di-... 

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