Journal of the American Ceramic Society Awards Symposium: Journal of the American Ceramic Society Awards Symposium II
Sponsored by: ACerS
Program Organizers: William Fahrenholtz, Missouri University of Science and Technology
Wednesday 2:00 PM
October 20, 2021
Room: B233
Location: Greater Columbus Convention Center
Session Chair: William Fahrenholtz, Missouri University of Science and Technology; Jonathon Foreman, American Ceramic Society
2:00 PM Invited
In-Situ Resistance Degradation & Switching of Bulk YSZ & STO Single Crystals: Ana Alvarez1; I-Wei Chen1; 1University of Pennsylvania
While Y-stabilized zirconia (YSZ) is a fast oxygen conductor and Fe-doped strontium titanate (STO) a p-type semiconductor, representing two extremes of oxide conductors, surprisingly their DC electrical degradation, or resistance breakdown, in highly accelerated lifetime tests (HALT) is phenomenologically indistinguishable. Our more detailed study, however, revealed that YSZ degrades by raising the electron chemical potential at the redox boundary to reach a two-phase, thermodynamic, metal-insulator transition level, even though the insulator side remains mostly unchanged. In contrast, STO forms a p-n junction by oxygen vacancy demixing, but the late-stage-demixing kinetics can be so sluggish that the steady state is not reached in low-temperature HALT. In STO, in particular, needle-like degradation paths often form, which explains the strong field dependence and large variation of lifetimes. These results provide new insight on related processes, such as flash sintering and melt processing of ceramics as well as resistance memory of oxide thin films.
2:30 PM Cancelled
Glassy Ga-Te Binaries: Structure and Properties for Phase-change Memory Applications: Andrey Tverjanovich1; Maria Bokova2; Chris Benmore3; Daniele Fontanari Fontanari2; Anton Sokolov2; Mohammad Kassem2; Maxim Khomenko4; Eugene Bychkov5; 1Institute of Chemistry, Saint Petersburg State University; 2Université du Littoral Côte d’Opale; 3Advanced Photon Source, Argonne National Laboratory; 4ILIT RAS−Branch of the FSRC “Crystallography and Photonics” RAS; 5Université du Littoral Côte d’Opale; ILIT RAS−Branch of the FSRC “Crystallography and Photonics” RAS
Telluride alloys Ge-Te and Ge-Sb-Te belong to flagship phase-change materials (PCMs) and are widely used for optical storage, nonvolatile memory applications and recently for neuromorphic computing. Surprisingly, a simple binary system Ga-Te remains virtually unexplored despite a chemical and electronic similarity to Ge-Te binaries.Unraveling the atomic structure of bulk Ga-Te glasses to follow their thermal, electrical and optical properties as well as transformation changes on phase-change transitions is the main goal of the present communication. High-energy X-ray diffraction and Raman spectroscopy supported by first-principles simulations are the efficient tools to elucidate the phase-change mechanisms and discover the critical features for reliable PCM operations. We will present both experimental electronic and structural results, and DFT and molecular dynamics modeling to fully characterize Ga-Te binaries and unravel their potential as a novel PCM system.
3:00 PM Break
3:30 PM Invited
Domain Walls in Ferroelectrics: Sukriti Mantri1; John Daniels1; 1University of New South Wales
Domain-walls in ferroelectrics have in past been predicted using analytical calculations wherein equations were solved for planes for which resolved strain from either side of domain-wall was equal on domain-wall plane. This method provides no information on the relative-energetics of non-ideal domain-walls. Here, we study the residual strain on every possible plane normal between two domains. We predict the permissible strain-free domain-walls along with the variation in residual domain-wall strain for non-permissible domain walls in ferroelectric symmetries of tetragonal, rhombohedral, orthorhombic and monoclinic(MA). It was found that the domain-walls in tetragonal and rhombohedral symmetry are fixed; Orthorhombic and monoclinic symmetries, in addition to fixed domain-walls, also have strange domain-walls(S-walls) that change their crystallographic plane as a function of distortion. The domains whose domain walls cannot be solved using analytical methods(R-walls), were shown to have almost permissible(negligible-strain) domain-walls. Changes in permissible domain wall orientation due to external stimuli was also predicted.
4:00 PM Invited
Relaxor Characteristics and Electromechanical Response under High Field for Sodium BismuthTtitanate-based Ceramics: Shuaishuai Bian1; Zhenxing Yue1; 1Tsinghua University
Bi0.5Na0.5TiO3 (BNT) is an important lead-free ferroelectric ceramic material. Due to their unique crystal structure, BNT-based ceramics usually have high remanent polarization, large coercive field and relaxor characteristics. Therefore, they can be promising candidates for piezoelectric actuators, dielectric energy storage capacitors, oxygen ion conductors, and etc. Recently, we made a series of modifications to the BNT ceramic material, and the structure and relaxor properties of the modified ceramics were analyzed thoroughly. An ultrahigh energy storage density (~4.77 J/cm3) and good stability of performance were achieved in the Bi0.5Na0.5TiO3-CaZr0.5Ti0.5O3 ceramics, possessing a fast discharge speed and high power density. In addition, a giant electro-strain (~2%) under high temperature was obtained in the relaxor BNT-based ceramics and the related mechanism was further demonstrated. This work is beneficial to expand the versatility of BNT-based materials and provide useful ideas to design high-performance lead-free ferroelectric and piezoelectric ceramics.
4:30 PM Concluding Comments