Phase Transformations in Ceramics: Science and Applications: Poster Session
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 11:00 AM
October 19, 2021
Room: Exhibit Hall B
Location: Greater Columbus Convention Center
P1-8: Structure, Electronic and Optical Properties of Ternary Nitride Phases of MgSnN2: A First-principles Study: Bishal Dumre1; Daniel Gall2; Sanjay Khare1; 1The University of Toledo; 2Rensselaer Polytechnic Institute
We have studied the disordered rocksalt, orthorhombic, and disordered wurtzite phases of the ternary nitride semiconductor MgSnN2 by first-principles methods using density functional theory (DFT) and beyond. The results imply that MgSnN2 is mechanically and dynamically stable in all three phases. However, pCOHP analysis suggests that the disordered rocksalt structure has antibonding states below the Fermi level between –5 eV and –2 eV, as compared to the bonding states in the other two phases, indicative of its thermodynamic metastability. Computed lattice constant and electronic band-gap values of 4.56 Å and 2.69 eV for MgSnN2 in the disordered rocksalt structure compare well with experimentally reported values of 4.48 Å and 2.3 eV, respectively. Furthermore, band gaps were computed for MgSnN2-xOx (x = 0.5, 1.0, 1.5, 2.0) to elucidate the role of possible oxygen impurities. Band-gap bowing is suggested to occur upon alloying with oxygen.
Poster
P1-9: Understanding the Effect of Aliovaent Doping on Phase Transformations and Thermo-physical Properties in RENbO4: Daniel Lowry1; Pankaj Sarin1; 1Oklahoma State University
In this study, the effect of the type and extent of A-site doping with divalent alkaline earth cations on the phase transformation and thermal properties of RENbO4 (RE = La, Dy) was investigated. Powder samples of La1-xMxNbO4-δ (M = Mg, Ca, Sr, Ba; x=0 to 0.02, in steps of 0.01) and Dy1-yMgyNbO4-δ (y = 0 to 0.05, in steps of 0.01) were synthesized by the stearic entrapment method. Specific heat capacity from differential scanning calorimetry, and high temperature X-ray diffraction were used to understand the phase transformations and thermal properties up to 1500°C. All the materials exhibited second order transformation, and aliovalent doping increased the transformation temperature. The t-DyNbO4 phase also showed order-disorder transformations at high temperatures, which decreased with increasing Mg2+ concentrations. Key results on change in lattice parameters, effect on the phase transformation, and thermal expansion will be presented as a function of composition and temperature.