Mapping of strain mechanisms in barium titanate by three-dimensional X-ray diffraction

Marta Majkut

Research output: Book/ReportPh.D. thesis

549 Downloads (Pure)


This thesis presents an in-situ three-dimensional study of the grain-scale response of a prototypical piezoelectric ceramic, barium titanate (BT), to an exernally applied electric field. Piezoceramics take advantage of the coupling of electrical and mechanical energies for use in sensors and actuators, found in both common applications such as fuel injectors and specialized applications such as medical imaging equipment. Since piezoceramics are typically used in the polycrystalline state it is important to consider not just the crystal structure but also the role of intergranular effects in the structure-properties relationships. Such effects are difficult to observe using destructive two-dimensionsional microscopy techniques and averaged over the entire sample in conventional powder diffraction studies. We instead use a combination of nondestructive three-dimensional X-ray diffraction techniques to study the material at the grain scale.
First, we use the intensity ratios of split diffraction peaks to extract grain-scale domain volume fractions for 139 grains. We find that even in the as-processed state there exist unequal volume fractions of each domain type, which we attribute to a heterogeneous local environment at the cubic to tetragonal transition during processing. When a field is applied, we observe a first-order orientation dependence with second order deviations, again attributed to the grain neighbourhood effect. Corellation of this with microstructural parameters such as grain size, neighbour misorientation and position within the sample did not reveal any obvious causes.
Next we develop a novel indexing and refinement method whereby the peak positions of domains are forward projected from crystallographic twinning orienations and the deviation between projected and measured diffraction patterns is minimized to refine domain-scale orientations and lattice parameters. We present the results of refinement for a bulk grain in which the domains are found to be misoriented from perfect crystallographic twins by 0.1-0.3°, suggesting a strained microstructure. The data set was collected by illuminating the entire width of the sample with a box beam, thus it contains a statistically significant number of grains for which domain-scale parameters will be refined in the future.
Original languageEnglish
PublisherDepartment of Physics, Technical University of Denmark
Number of pages159
Publication statusPublished - 2016


Dive into the research topics of 'Mapping of strain mechanisms in barium titanate by three-dimensional X-ray diffraction'. Together they form a unique fingerprint.

Cite this