In-situ XRD study of actuation mechanisms in BiFeO3-K0.5Bi0.5TiO3-PbTiO3 ceramics

Abstract

In the present study, we report a nonergodic relaxor ferroelectric composition for high temperature piezoelectric applications, 0.57BiFeO 3-0.21K 0.5 Bi 0.5 TiO 3-0.22PbTiO 3 , which exhibits T m around 420 °C. By combining the results of in-situ synchrotron XRD and strain measurements using digital image correlation, a pseudocubic nonergodic relaxor to rhombohedral ferroelectric transformation is identified, accompanied by a volume strain close to zero. A methodology is developed to determine the crystallographic parameters of the transformed rhombohedral ferroelectric phase in a strain-free state, using the invariant intersection for diffraction stress analysis. The phase transformation process was analyzed by methods combining peak profile fitting and full pattern refinement; the results obtained illustrate the strain arising from the phase transformation, together with intrinsic/extrinsic contributions and anisotropy in the field-induced strain. The study reveals unusual microscopic strain behavior, distinguished from that of normal rhombohedral ferroelectrics, showing the combined properties of ergodic and normal ferroelectric materials and leading to a dominant intrinsic lattice strain together with a weaker extrinsic domain switching effect. The elastic coupling between different grain families is also reflected in their similar strain orientation distribution (SOD) functions.

Understanding the Nature of Temperature Stability in Potassium Sodium Niobate Based Ceramics from Structure Evolution under External Field

“…In this work, three kinds of XRD measurements were designed. Rietveld refinement on XRD data was carried out on the KNNS–BKH powder measured at different temperatures (20–200 °C) to analyze the intrinsic structure information without any influence of external electric fields, during which Findit and MAUD software were employed. − For better illustration of the in situ d 33 , the in situ XRD of the poled samples was measured from 20 to 250 °C. And the XRD patterns of the samples after they were poled at 20, 50, 70, and 100 °C were also measured.…”

Origin of the large electrostrain in BiFeO3-BaTiO3 based lead-free ceramics

“…Macroscopic structural transformations in perovskites are characterised by changes in {111} p and {200} p peak profiles prior to and after application of the field. [19][20][21][22][23][24][25] Initially, in this contribution, the macroscopic strain is evaluated by observation of {111} p , {200} p and {220} p peaks at 60 kV cm -1 with a step of 5 kV cm -1 . [12,19] Measurements parallel (β = 0°) and perpendicular (β = 90°) to the direction of the field illustrate any domain re-orientation and associated lattice strain.…”

“…[15,28] The domain switching behaviour in polycrystalline ferroelectric ceramics leads to anisotropic dimensional deformation, as well as lattice strain. According to Jones and co-workers [20,21,28], the spontaneous strain for single crystal distortion associated with non-180° domain switching for a rhombohedral cell can be defined as follows:…”

“…XRD patterns for each azimuthal section are obtained via in-situ poling experiments to determine the peak intensities and peak position. η for the R3c phase is calculated using Jones' method [20,28].…”

Photosynergy of Ag In Situ Anchored on AgNb1–xTaxO3 Solid Solutions as an Efficient and Durable Catalyst toward Nitrobenzene Reduction: Uncovering the Relevance of the Electronic Structure, Active Sites, and Catalytic Activity

“…It has been reported that Ta doping greatly accelerated the crystal growth, which leads to certain sets of split diffraction peaks in AgNb 1– x Ta x O 3 gradually converging into single peaks (Figure S1). − All Bragg reflections shift toward higher angles, including 2θ at 22.6 and 52.1°, which generally leads to a shrinking lattice volume and a different electronic structure. , Therefore, it is significant to know about the mechanism of the doping effect in niobium and tantalum solid solutions.…”