Advances in Powder and Ceramic Materials Science: High Entropy Ceramics II
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS: Materials Characterization Committee, TMS: Powder Materials Committee
Program Organizers: Bowen Li, Michigan Technological University; Dipankar Ghosh, Old Dominion University; Eugene Olevsky, San Diego State University; Kathy Lu, University of Alabama Birmingham; Faqin Dong, Southwest University of Science and Technology; Jinhong Li, China University of Geosciences; Ruigang Wang, Michigan State University; Alexander Dupuy, University of Connecticut
Monday 2:00 PM
March 20, 2023
Room: 30A
Location: SDCC
Session Chair: William Bowman, University of California Irvine; Stefano Curtarolo, Duke University
2:00 PM Introductory Comments
2:05 PM Invited
Multifunctional High-entropy Ceramics: Stefano Curtarolo1; Corey Oses1; Cormac Toher2; Arrigo Calzolari3; Marco Esters1; 1Duke University; 2U. Texas Dallas; 3CNR
This presentation is devoted to the discussion of recent advances in designing of high-entropy ceramics with applications in mind.
2:25 PM
Dislocation-based Room Temperature Plasticity in High Entropy Oxides: Xin Wang1; Justin Cortez1; Alexander Dupuy1; William Bowman2; Julie Schoenung1; 1University of California Irvine; 2University of California Irvine; Irvine Materials Research Institute
Dislocations are common in metals, but their importance has not been fully recognized in ceramics. As a new class of materials, high entropy oxides (HEOs) have attracted significant interest due to their entropy-enhanced stability and compositionally tunable properties, which are required for various functional and structural applications. Here, we explore room temperature deformation mechanisms of (Co,Cu,Mg,Ni,Zn)O HEOs using nanoscratch and micropillar compression tests. The deformation microstructures after controlled deformation were systematically characterized using scanning/ transmission electron microscopy (S/TEM). We observe that, unlike most ceramics, HEOs with micron-sized grains exhibit prominent dislocation activity during room temperature deformation. The dislocation density observed can reach 1014 m-2, which is comparable with cold-worked alloys. In contrast, nanocrystalline samples exhibit intergranular crack propagation and grain boundary sliding, indicating that the mechanical behavior of HEOs can be tailored through microstructure. Orientation-dependent slip activation was further investigated to provide insights into the plastic anisotropy of this material.
2:45 PM
Mechanical Behavior of Multiphase Entropy Stabilized Oxides: Salma El-Azab1; Luz Gomez1; Alexander Dupuy1; Julie Schoenung1; 1University of California Irvine
Entropy stabilized oxides (ESOs) undergo a reversible phase transformation between a multiphase and a single phase state. (Co,Cu,Mg,Ni,Zn)O transition metal ESOs (TM-ESOs) exhibit a rocksalt phase, plus Cu-rich tenorite and Co-rich spinel secondary phases that form during heat treatment. The role of these secondary phases on the mechanical behavior is not currently understood. The present investigation seeks to harnesses this phase transformation to tailor the mechanical behavior of TM-ESOs. Sintered single-phase samples were heat treated for different time increments to form variable secondary phase concentrations. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy were employed to characterize secondary phase evolution. Room temperature indentation experiments were performed to evaluate the hardness, elastic modulus, and fracture toughness. Because the secondary phases exhibit different mechanical behavior than the TM-ESO rocksalt phase, Cu-deficient and Co-deficient compositions were also analyzed to isolate the influence of individual secondary phases on mechanical behavior.
3:05 PM
Enhanced Li-ion Conductivity in Compositionally Complex Perovskite Oxides: Shu-Ting Ko1; Dawei Zhang1; Tom Lee2; Ji Qi1; Shyue Ping Ong1; Xiaoqing Pan2; Jian Luo1; 1University of California, San Diego; 2University of California, Irvine
Solid oxide electrolytes are promising for next-generation rechargeable batteries due to their nonflammability and rigidity in preventing dendrite penetration, but they often suffer from high grain boundary resistance. Notably, the perovskite-type Li0.375Sr0.4375Ta0.75Zr0.25O3 (LSTZ) exhibits one-order higher grain boundary Li-ion conductivity compared to the well-known Li3xLa2/3 − x□1/3−2xTiO3; however, its bulk ionic conductivity can be further improved. Herein, we report new compositionally complex perovskite oxides (CCPOs) which show higher bulk ionic conductivity than LSTZ, along with improved phase stability. The negligible grain boundary resistance is attributed to the enhanced grain growth as observed by electron backscattered diffraction and vacancies at grain boundaries. Finally, a moment tensor potential (MTP) of a CCPO is developed to simulate both bulk and grain boundary structures, enabling the studies of Li-ion diffusivities and surface energies. The present work demonstrates a new possibility of developing medium- and high-entropy compositionally complex ceramics (CCCs) in energy storage applications.
3:25 PM
Dual Cubic Perovskite Phases in Macro-Equimolar High Entropy Oxides: Imrongnaro Longkumer1; Ashutosh Gandhi1; 1IIT Bombay
The multicomponent equimolar oxides (MEO) ceramics having 6-8 different components have been synthesized using the solution combustion method. The chosen cations are Al3+, Ba2+, Ca2+, Cr3+, Gd3+, La3+, Sr2+, Ti4+ and Zr4+. The cations are selected for each composition based on the Pauling’s rules and having the theoretical calculation of Goldschmidt’s tolerance factor between 0.9 to 1.2. For all the compositions, we obtain two phases with the cubic perovskite structure of different lattice parameters. A couple of compositions contain additional phases. The formation of the dual cubic perovskite phases in each composition is examined. Structure determination from powder X-ray diffraction was carried out using Rietveld refinement. HRTEM imaging and EDS was used to identify the elemental composition of the dual cubic phases. Dielectric, fracture toughness and thermal conductivity properties were measured and found to show interesting results.