ORCID Profile
0000-0002-6482-3570
Current Organisation
Iran University of Science and Technology
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Publisher: Springer Science and Business Media LLC
Date: 09-03-2016
DOI: 10.1038/SREP22820
Abstract: Understanding coupling of ferroic properties over grain boundaries and within clusters of grains in polycrystalline materials is hindered due to a lack of direct experimental methods to probe the behaviour of in idual grains in the bulk of a material. Here, a variant of three-dimensional X-ray diffraction (3D-XRD) is used to resolve the non-180° ferroelectric domain switching strain components of 191 grains from the bulk of a polycrystalline electro-ceramic that has undergone an electric-field-induced phase transformation. It is found that while the orientation of a given grain relative to the field direction has a significant influence on the phase and resultant domain texture, there are large deviations from the average behaviour at the grain scale. It is suggested that these deviations arise from local strain and electric field neighbourhoods being highly heterogeneous within the bulk polycrystal. Additionally, the minimisation of electrostatic potentials at the grain boundaries due to interacting ferroelectric domains must also be considered. It is found that the local grain-scale deviations average out over approximately 10–20 grains. These results provide unique insight into the grain-scale interactions of ferroic materials and will be of value for future efforts to comprehensively model these and related materials at that length-scale.
Publisher: Elsevier BV
Date: 09-2015
Publisher: Wiley
Date: 12-09-2016
DOI: 10.1111/JACE.14481
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 10-2013
Publisher: IOP Publishing
Date: 02-11-2015
Publisher: International Union of Crystallography (IUCr)
Date: 22-05-2015
DOI: 10.1107/S1600576715007669
Abstract: A method for the extension of the three-dimensional X-ray diffraction technique to allow the extraction of domain volume fractions in polycrystalline ferroic materials is presented. This method gives access to quantitative domain volume fractions of hundreds of independent embedded grains within a bulk s le. Such information is critical to furthering our understanding of the grain-scale interactions of ferroic domains and their influence on bulk properties. The method also provides a validation tool for mesoscopic ferroic domain modelling efforts. The mathematical formulations presented here are applied to tetragonal coarse-grained Ba 0.88 Ca 0.12 Zr 0.06 Ti 0.94 O 3 and rhombohedral fine-grained (0.82)Bi 0.5 Na 0.5 TiO 3 –(0.18)Bi 0.5 K 0.5 TiO 3 electroceramic materials. The fitted volume fraction information is used to calculate grain-scale non-180° ferroelectric domain switching strains. The absolute errors are found to be approximately 0.01 and 0.03% for the tetragonal and rhombohedral cases, which had maximum theoretical domain switching strains of 0.47 and 0.54%, respectively. Limitations and possible extensions of the technique are discussed.
Publisher: International Union of Crystallography (IUCr)
Date: 08-2014
DOI: 10.1107/S160057671401406X
Abstract: A comparison of the performance of X-ray diffraction tomography, a near-field diffraction technique, and a far-field diffraction technique for indexing X-ray diffraction data of polycrystalline materials has been carried out by acquiring two sets of diffraction data from the same polycrystalline s le volume. Both approaches used in this study are variants of the three-dimensional X-ray diffraction (3DXRD) methodology, but they rely on different data-collection and analysis strategies. Previous attempts to assess the quality of 3DXRD indexing results from polycrystalline materials have been restricted to comparisons with two-dimensional electron backscatter diffraction cross sections containing a limited number of grains. In the current work, the relative performance of two frequently used polycrystalline-material indexing algorithms is assessed, comparing the indexing results obtained from a three-dimensional s le volume containing more than 1500 grains. The currently achievable accuracy of three-dimensional grain maps produced with these algorithms has been assessed using a statistical analysis of the measurement of the size, position and orientation of the grains in the s le. The material used for this comparison was a polycrystalline commercially pure titanium grade 2 s le, which has a hexagonal close-packed crystal structure. The comparison of the two techniques shows good agreement for the measurements of the grain position, size and orientation. Cross-validation between the indexing results shows that about 99% of the s le volume has been indexed correctly by either of these indexing approaches. The remaining discrepancies have been analysed and the strengths and limitations of both approaches are discussed.
Publisher: Elsevier BV
Date: 05-2015
Location: Iran (Islamic Republic of)
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Ayat Gharehghani.