Crystallization Processes of Heterogeneous Systems Followed in Time Resolved X-ray Powder Diffraction

1990 ◽  
Vol 205 ◽  
Author(s):  
Axel NØrlund Christensen
Keyword(s):  
Powder Diffraction ◽  
Heterogeneous Systems ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
Reaction Products ◽  
Time Resolved ◽  
X Ray ◽  
Powder Diffractometer ◽  
Position Sensitive

AbstractTime resolved X-ray powder diffraction was used to follow the crystallization processes in the systems MgO-MgCl2-H2O and MgO-H2O. A Stoe X-ray powder diffractometer with a position sensitive detector was used. The crystalline reaction products are [Mg2(OH)3(H2O)2]C1.H2O and Mg(OH)2 dependent upon the MgC12 concentrations in the heterogeneous systems. Mg(OH)2 was the product in a 1.50 M MgCl2 solution and [Mg2(OH)3(H2O)3]Cl.H2O was formed in 3.00 and 5.17 M MgCl2 solutions at 20°C.

High-resolution synchrotron X-ray powder diffraction with a linear position-sensitive detector

1988 ◽  
Vol 21 (6) ◽  
pp. 905-910 ◽  
Author(s):  
M. S. Lehmann ◽  
A. N. Christensen ◽  
M. Nielsen ◽  
R. Feidenhans'l ◽  
D. E. Cox
Keyword(s):  
High Resolution ◽  
Powder Diffraction ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray ◽  
Position Sensitive

Synthesizing and fitting linear position-sensitive detector step-scanned line profiles

1994 ◽  
Vol 27 (5) ◽  
pp. 673-681 ◽  
Author(s):  
R. W. Cheary ◽  
A. Coelho
Keyword(s):  
Incident Beam ◽  
Position Sensitive Detector ◽  
Physical Parameters ◽  
Sensitive Detector ◽  
X Ray ◽  
Powder Diffractometer ◽  
Experimental Step ◽  
Position Sensitive ◽  
Scan Data ◽  
Counting Statistics

An X-ray powder diffractometer has been modified by the addition of a narrow-bandpass germanium pre-monochromator and a linear position-sensitive detector (LPSD) with its centre set at the normal θ–2θ focusing condition. Diffraction data are recorded using a step-scan procedure in which the patterns recorded at each step are summed to form the final pattern over a wide angular range. In this way, diffraction patterns covering 120 2θ can be recorded 100 times more rapidly than with conventional receiving-slit diffractometers for the same level of counting statistics. In this paper, an analysis has been carried out of the contribution of the instrumental parameters to the shapes of the X-ray diffraction lines obtained with either a stationary or a step-scanned LPSD. This is done by calculating theoretical profiles for defocusing, parallax error, thermal-noise broadening and LPSD pixel size and convoluting them with the Cu Kα emission spectrum and aberration profiles associated with a standard focusing powder diffractometer. Theoretical profiles for fitting to experimental step-scan data are synthesized by summing convoluted profiles across the detector window. The validity of this procedure is tested by fitting to experimental step-scan data from well characterized reference specimens of MgO and Y3Al5O12 (YAG). The extra broadening associated with the inclusion of a LPSD is refined in terms of the depth of the detector, the angular window of the LPSD and the angle of divergence of the incident beam. Good fits have been obtained to the reference profiles and the physical parameters of the diffractometer determined in this way agree well with directly measured values.

Time-Resolved Observations of Solid Reactions and Structure Transitions using a PSD, An SSD and Computer Aided Measurement and Control

1991 ◽  
Vol 35 (A) ◽  
pp. 415-423 ◽  
Author(s):  
Takamitsu Yamanaka ◽  
Shinji Kawasaki ◽  
Tsuyoshi Shibata
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Counting Efficiency ◽  
Energy Dispersive ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
Time Resolved ◽  
Kinetic Information ◽  
Dehydration Reactions ◽  
Position Sensitive

AbstractFor time-resolved diffraction studies under high temperature and/or high pressure, we designed a new diffractometer incorporating a curved position sensitive detector and tested the rapid intensity measurement and the resolution of the angular dispersive diffraction. The diffraction profiles were compared with those from energy dispersive diffraction. Rapid intensity collection has been carried out with a CAMAC module. A curved position sensitive detector with a 120° working angular region was installed on the off-centered four circle diffractometer. Only a few seconds were needed to obtain a whole powder diffraction because of the extremely high counting efficiency due to the streamer mode.Time-resolved observations of the dehydration reactions of Mg(OH)2 and Ca(OH)2, have been undertaken by angular dispersive and energy dispersive x-ray powder diffraction at high temperature. The in situ observations of the dehydration process provide kinetic information, such as the reaction rate, the apparent activation energy and the dehydration mechanism.

The Use and Accuracy of Continuously Scanning Position-Sensitive Detector Data in X-Ray Powder Diffraction

1980 ◽  
Vol 24 ◽  
pp. 123-138 ◽  
Author(s):  
Herbert E. Göbel
Keyword(s):  
Powder Diffraction ◽  
Position Sensitive Detector ◽  
Good Resolution ◽  
X Rays ◽  
Sensitive Detector ◽  
Accumulation Time ◽  
X Ray ◽  
Lattice Constants ◽  
Position Sensitive

AbstractBy collecting the diffracted X-rays in a focussing powder diffractometer with a linear position-sensitive detector (PSD), the data accumulation time can be widely reduced. Due to the focussing properties of the geometrical arrangement good resolution can be simultaneously achieved over a few degrees of the diffraction angle 2 Theta. The full pattern is collected by scanning the PSD along the entire 2 Theta arc. Scanning speeds of several hundred degrees per minute are possible and still yield well plotted diagrams.This work demonstrates the performance of the system in different tasks of X-ray powder diffraction such as identification of unknown materials, quantitative analysis, determination of lattice constants and microcrystalline properties. The results, evaluated by parts of the program system DIFFRAC 11, show that the accuracy and resolution of the continuously scanning PSD technique match these tasks without difficulty and reach the precision limits of powder diffractometry itself. It is demonstrated that the data collection velocity, which matches well the data evaluation times, is not the only advantage compared to conventional diffractometets.

Control of the phase composition of advanced calcium phosphates using an x-ray diffractometer with a curved position-sensitive detector

2020 ◽  
Vol 86 (6) ◽  
pp. 29-35
Author(s):  
V. P. Sirotinkin ◽  
O. V. Baranov ◽  
A. Yu. Fedotov ◽  
S. M. Barinov
Keyword(s):  
Phase Composition ◽  
Calcium Phosphates ◽  
Position Sensitive Detector ◽  
Sensitive Detector ◽  
X Ray Diffraction ◽  
X Ray ◽  
Impurity Phases ◽  
Position Sensitive ◽  
Diffraction Peaks ◽  
Diffraction Patterns

The results of studying the phase composition of advanced calcium phosphates Ca10(PO4)6(OH)2, β-Ca3(PO4)2, α-Ca3(PO4)2, CaHPO4 · 2H2O, Ca8(HPO4)2(PO4)4 · 5H2O using an x-ray diffractometer with a curved position-sensitive detector are presented. Optimal experimental conditions (angular positions of the x-ray tube and detector, size of the slits, exposure time) were determined with allowance for possible formation of the impurity phases during synthesis. The construction features of diffractometers with a position-sensitive detector affecting the profile characteristics of x-ray diffraction peaks are considered. The composition for calibration of the diffractometer (a mixture of sodium acetate and yttrium oxide) was determined. Theoretical x-ray diffraction patterns for corresponding calcium phosphates are constructed on the basis of the literature data. These x-ray diffraction patterns were used to determine the phase composition of the advanced calcium phosphates. The features of advanced calcium phosphates, which should be taken into account during the phase analysis, are indicated. The powder of high-temperature form of tricalcium phosphate strongly adsorbs water from the environment. A strong texture is observed on the x-ray diffraction spectra of dicalcium phosphate dihydrate. A rather specific x-ray diffraction pattern of octacalcium phosphate pentahydrate revealed the only one strong peak at small angles. In all cases, significant deviations are observed for the recorded angular positions and relative intensity of the diffraction peaks. The results of the study of experimentally obtained mixtures of calcium phosphate are presented. It is shown that the graphic comparison of experimental x-ray diffraction spectra and pre-recorded spectra of the reference calcium phosphates and possible impurity phases is the most effective method. In this case, there is no need for calibration. When using this method, the total time for analysis of one sample is no more than 10 min.

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