Phase Transformations in Ceramics: Science and Applications: Computation and Predictions
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
Tuesday 2:00 PM
October 19, 2021
Room: B230
Location: Greater Columbus Convention Center
2:00 PM
Effects of S Doping on the Mechanical and Opto-electronic Properties of Cu2CdGeSe4: Victor Barone1; Bishal Dumre1; Randall Ellingson1; Sanjay Khare1; 1The University of Toledo
We have used first principles density functional theory to report on the effects of S doping on the mechanical and optoelectronic properties of the Cu2CdGeSe4 in it’s two known crystal structures. Computed lattice parameters (a,b,c, in Å) and band gaps (E_g, in eV) of tetragonal (I-42m) Cu2CdGeSe4 (a=5.85,c=11.25,E_g=1.18), orthorhombic (Pmn21) Cu2CdGeSe4 (a=6.70,b=6.99,c=8.21,E_g=1.26), and orthorhombic Cu2CdGeS4 (a=6.36,b=6.63,c=7.78,E_g=1.85) match well with experimental values: (a=5.75,c=11.12,E_g=1.20) for tetragonal Cu2CdGeSe4, (a=6.60,b=6.88,c=8.06,E_g=1.27) for orthorhombic Cu2CdGeSe4, and (a=6.30,b=6.56,c=7.71,E_g=1.93) for orthorhombic Cu2CdGeS4. Additionally, our calculations predict that the tetragonal-phase Cu2CdGeS4 should be stable, although no reports of this material exist. The computed formation energy for tetragonal phase is lower than orthorhombic. This ordering of energies is consistent with experimental observation that the growth temperature for the tetragonal phase reported is 200 ℃ lower than orthorhombic. Our optical property calculations and band gap values imply that this system could be suitable for applications as a solar cell absorber material.
2:20 PM
Nanostructured Spinel Ferrite Ceramics: Structure and Magnetic Properties: Suraj Mullurkara1; Y. Wang1; A. Talaat1; W. Xiong1; J.K. Lee1; P.R. Ohodnicki1; 1University of Pittsburgh
Nanostructuring of bulk Co-Fe-O spinel ferrites via spinodal decomposition is known to have an impact on magnetic behavior through nm-scale microstructural fluctuations in chemical composition and local stress. In this work, we explore effects of decomposition in bulk Co-Fe spinel ferrite. Thermodynamic calculations are presented using Thermo-Calc based databases and analytical modeling techniques. Traditional powder processing techniques including planetary ball milling followed by calcination and thermal annealing were used to produce spinodally decomposed cobalt ferrite. Structural characterization is performed using x-ray diffraction and vibrating sample magnetometry was utilized to study effects of decomposition on magnetic properties including First order reversal curve (FORC) analysis. Finally, M-H loop measurements combined with FORC distributions were used to investigate the dominant magnetic interactions and reversal mechanisms in the material.