Phase Transformations in Ceramics: Science and Applications: Experimental Studies on Structure and Control I
Sponsored by: ACerS Basic Science Division, ACerS Electronics Division, ACerS Engineering Ceramics Division
Program Organizers: Scott Mccormack, University Of California, Davis; Pankaj Sarin, Oklahoma State University; Sanjay V. Khare, University of Toledo; Waltraud Kriven, University of Illinois at Urbana-Champaign
Monday 8:00 AM
October 18, 2021
Room: B230
Location: Greater Columbus Convention Center
8:00 AM Invited
Electrical Activation of the Martensitic Transformation in Zirconia: Christopher Schuh1; Alan Lai1; 1Massachusetts Institute of Technology
The martensitic transformation in zirconia has been extensively studied for its role in transformation toughening, shape memory, and superelasticity. This talk will review our recent work exploring the coupling of electric field with this transformation. Although both phases (tetragonal and monoclinic) are centrosymmetric and therefore not intrinsically electrically polarized, they are both polarizable under field with significantly different electrical susceptibilities. As a result, when a field is applied in the monoclinic (low temperature) phase, there is an electrical driving force that favors the transition to the tetragonal (high temperature) phase. We establish this unique activation mode for martensitic transformation through in-situ x-ray diffraction experiments on bulk single crystal specimens, and verify its reversibility and reproducibility. Clausius-Clapeyron analysis is used to develop the form of the phase diagram, which features a transus temperature that is parabolic with respect to electric field. This unusual scaling and its corollary implications are also discussed.
8:30 AM Invited
Tailorable Porous CeO2-Doped ZrO2 as a Pathway to Superelastic and Shape-memory Ceramics: Laura Quinn1; Katherine Faber1; 1California Institute of Technology
Although zirconia-based materials were known to exhibit shape-memory and superelastic effects more than 30 years ago, successful application of these phenomena was impeded due to martensitic transformation-induced volume changes that result in fracture. Studies in the last decade, however, demonstrated that single- or oligocrystalline micropillars, loose particles, and nanofibers can accommodate the volume change of the tetragonal-to-monoclinic transformation, and thus avoid fracture. Inspired by these studies, we developed a freeze-casting method to produce a porous zirconia-based ceramic which combines oligocrystalline pore walls in a honeycomb-like bulk structure, thereby averting transformation-generated fracture. Composition control is afforded through a sol-gel synthesis of CeO2-ZrO2 which allows for uniform distribution of ceria throughout the zirconia. Furthermore, the ceria content can be varied to explore both superelastic and shape-memory behaviors. The martensitic transformation is tracked during compression testing and by Raman spectroscopy and X-ray diffraction.
9:00 AM
Useful Energy Dissipation and Fatigue Resistance in Cyclically Loaded Superelastic Ceramic Granular Packings: Hunter Rauch1; Joey Griffiths1; David Garcia1; Yan Chen2; Ke An2; Hang Yu1; 1Virginia Polytechnic Institute and State University; 2Oak Ridge National Lab
Zirconia-based superelastic ceramics possessing a reversible martensitic transformation have large stress-strain hysteresis which can be a design tool when viewed as a sink for mechanical energy. These materials undergo large strains during transformation and are prone to brittle failure, so material forms with low mechanical constraint, like granular packings, are necessary. In granular form, superelastic ceramics exhibit a ‘continuous mode’ of transformation due to the heterogeneous nature of stress distribution in the packing. Combining the continuous mode transformation with the large hysteresis yields a promising candidate for mechanical energy dissipation, where even small applied loads can result in some degree of transformation. Here, we present the first study of cyclic transformation in granular packings of superelastic zirconia, including results from in situ neutron diffraction and mechanical testing. We explore the evolution of the energy dissipation behavior over 10,000 loading cycles and find that the packings are resistant to functional fatigue.
9:20 AM
In-situ TEM Observation on the Motion of Phase Boundaries during Antiferroelectric ↔ Ferroelectric Transition: Binzhi Liu1; Xinchun Tian1; Lin Zhou2; Xiaoli Tan1; 1Iowa State University; 2U.S. Department of Energy
In-situ biasing transmission electron microscopy (TEM) was applied on a FIB-machined antiferroelectric Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98}O3 thin foil. The unique TEM holder equipped with an electrode probe is capable of recording current when the bias is employed. The probe was manipulated to contact the edge of the TEM specimen, and the displacive phase transition is explored. An area of radius of ~100 nm composed of multiple nuclei is observed, which is the critical size of nucleation, accompanied by a current spike due to the antiferroelectric phase transiting to the ferroelectric phase. It is noticed that the motion of the interphase boundary displays a strong crystallography dependence. In a [001]c oriented grain, two nonadjacent segments alone (010)c planes of a pre-existed ferroelectric domain moved together and merged, with the rapid consumption of (100)c plane segment. For another [-111]c oriented grain, the interface boundary moved apparently along <-1-10>c with different velocities.
9:40 AM
Critical Parameters Controlling the Formation of High-entropy Oxides: Kuo-Pin Tseng1; Benjamin Hulbert1; Qun Yang1; Waltraud Kriven1; 1University of Illinois at Urbana-Champaign
The formation of a multi-component system often suffers from phase separation during synthesis, resulting in multiple phases instead of single-phase materials. In high-entropy oxides, multiple cations should be constrained in a single-phase solid solution with homogeneous distribution. In formation of high-entropy oxides, both size mismatch and valance configuration among constituent cations have significant effects. Two lanthanide systems were designed to reveal the influence between these key parameters and the final oxide structures. The results demonstrate that a large mismatch in cations could trigger the failure in single-phase formation. On the other hand, the crystal structures of high-entropy oxides be modified by the preferred valence configurations of constituent cations. Here, this research provided a protocol for cation selection in order to synthesize high-entropy ceramics and explore the next generation of structure-stabilized ceramics.
10:00 AM Break
10:20 AM
Thermal Expansion and Phase Transformation in the Rare Earth Di-titanate System: Benjamin Hulbert1; Scott Mccormack2; Kuo-Pin Tseng1; Waltraud Kriven1; 1University of Illinois at Urbana-Champaign; 2University of California Davis
Characterization of the thermal expansion in the rare earth di-titanates is important for their use in high-temperature piezoelectric and dielectric applications. The thermal expansions of most rare-earth di-titanates, R2O3•2TiO2 (R = La, Pr, Nd, Sm, Gd, Dy, Er, Yb, Y), in both the monoclinic and cubic room temperature phases, were measured from room temperature to 1600℃. La2O3•2TiO2 undergoes a monoclinic to orthorhombic displacive transition on heating. The crystallographic orientation relation between these structures were studied. Crystalline powder samples were synthesized by the solution-based steric entrapment method. High temperature characterization was achieved with a quadrupole lamp furnace and 3-D thermal expansion coefficients leading to transformation mechanisms were obtained from in-situ synchrotron (APS-33BM-C) and neutron (SNS-BL11A) diffraction. Accurate temperature was determined using Pt as an internal temperature standard. Upon determination of the lattice parameters, the thermal expansion tensor was calculated and visualized using the program CTEAS.