Identification Of Minor Phases Research Articles

Titanium doping of BiFeO3 ceramics and identification of minor phases by Raman spectroscopy

Titanium substitution can improve the multiferroic properties of bismuth ferrite materials, albeit the structural changes that this dopant produces in the perovskite structure of BiFeO3 are still not well understood. Due to its high sensitivity, Raman spectroscopy can be a useful tool for trailing the dopant incorporation. In this work, we study the Raman spectra of undoped and Ti4+‐doped BiFeO3 ceramics that also contain small amounts of secondary phases – as it is usual for materials of this system. The micro‐Raman study together with a rigorous derivative analysis of the experimental Raman spectra recorded at low temperature (73 K) enables, for the first time, the identification of the Raman bands associated with the BiFeO3 phase together with those belonging to the minor secondary phases. The comparison between the Raman spectra of the undoped and the Ti4+‐doped materials indicates that some of the titanium added to the composition interacts with the secondary phases while only a partial amount of this dopant actually incorporates into the BiFeO3 phase. Copyright © 2017 John Wiley & Sons, Ltd.

Some Successful Approaches to Quantitative Mineral Analysis as Revealed by the 3rd Reynolds Cup Contest

AbstractDetails of the quantitative techniques successfully applied to artificial rock mixtures distributed for the third Clay Minerals Society Reynolds Cup (RC) contest are presented. Participants each received three samples, two containing 17 minerals each and a third containing ten minerals. The true composition of the samples was unknown to all participants during the contest period. The results submitted were ranked by summing the deviations from the actual compositions (bias). The top three finishers used mainly X-ray diffraction (XRD) for identification and quantification. The winner obtained an average bias of 11.3% per sample by using an internal standard and modified single-line reference intensity ratio (RIR) method based on pure mineral standards. Full-pattern fitting by genetic algorithm was used to measure the integrated intensity of the diagnostic single-line reflections chosen for quantification. Elemental-composition optimization was used separately to constrain phase concentrations that were uncertain because the reference mineral standards were lacking or not ideal. Cation exchange capacity, oriented-sample XRD analysis, and thermogravimetric analysis were also used as supplementary techniques. The second-place finisher obtained an average bias of 13.9%, also by using an RIR method, but without an added internal standard and with intensity measured by whole-pattern fitting. The third-place finisher, who obtained an average bias of 15.3%, used the Rietveld method for quantification and identification of minor phases (using difference plots). This participant also used scanning electron microscopy (with X-ray microanalysis) to identify minor components and verify the composition of structures used in Rietveld analysis. As in the previous contests, successful quantification appears to be more dependent on analyst experience than on the analytical technique or software used.

Crystallographical Analysis of Intermediate Phases in BI(2223)/AG Tape

Abstract (Bi,Pb)2Sr2Ca2Cu3Ox/Ag composite tapes are currently the most promising high-temperature superconductors for large-scale applications. A major issue in further improving the supercurrent-carrying-capability and optimizing fabrication procedures of these tapes is to understand the formation kinetics of the Bi(2223) from precursor powders of Bi(2212), CaO, and CuO. Since the microstructural transformation during the complicated phase evolution is not well known yet, identification of minor phases at different transformation stage is desirable. Here, we report our crystallographic analysis of several frequently observed intermediate phases during the phase evolution. The heat treatment of the tapes consisted of ramping the temperature to 840°C in air and of holding it for a prescribed period and then oil-quenching from various temperatures.

Diffrac-at Search: Search/Match Using Full Traces as Input

AbstractThe advantages of using the full trace as input for search/match rather than the traditional list of d/I values are emphasized. These advantages stem from the availability and the logical employment of the whole information of the diffractogram.The two key features which enable successful identification of minor phases are discussed: (1) the reliable discrimination between background and weak lines and (2) by regarding the actual full widths of major lines as regions where weak lines can, potentially, he obscured.The user friendliness of the. package will be presented: the graphical user interface, the high level of interactivity, and the speed of the search/match - now less than 8 seconds for searching the current whole ICDD database of 61,993 reference patterns when using an i486/66-based PC.

An Automated X-Ray Diffractometer for Detection and Identification of Minor Phases

In the preceding volume in this series, we described a stepping motor automation package for XRD data acquisition, based on the Apple microcomputer with an interface card that produces the stepping motor pulses and counts X-ray pulses from the normal X-ray detector and amplifier. We are presently using the system to automate a General Electric XRD-5 diffractometer mechanism, by replacing the original synchronous motor with the stepping motor, and installing 10:1 reduction gear instead of the chain drive to drive the double worm gears. This gives 2500 steps of the motor per degree two theta. Motor pulses are counted by a small machine language routine which also handles accelerating the mechanism when slewing over long angular ranges.