Congratulations to Dennis and colleagues on their publication in Scientific Reports, Electronic and Magnetic Properties of Lanthanum and Strontium Doped Bismuth Ferrite: A First-Principles Study.
Author: Trujillo, Dennis
Co and Nayak published in Phys. Rev. B
Great work Kevin and Dr. Nayak! They published in Physical Review B, Polarization rotation in Bi4Ti3O12 by isovalent doping at the fluorite sublattice.
Abstract
Bismuth titanate, Bi4Ti3O12 (BiT), is a complex layered ferroelectric material that is composed of three perovskitelike units and one fluoritelike unit stacked alternatively along the transverse direction. The ground-state crystal structure is monoclinic with the spontaneous polarization (∼50μC/cm2) along the plane. BiT typically grows along the c direction in thin-film form, and having the polarization vector aligned with the growth orientation can be beneficial for several potential device applications. It is well known that judicious doping of ferroelectrics is an effective method in adjusting the magnitude and the orientation of the spontaneous polarization. Here, we show using first-principles density-functional theory and a detailed phonon analysis that Bi atoms in the fluoritelike layers have significantly more impact on the magnitude and orientation of the spontaneous polarization vector as compared to the perovskitelike layer. The low-energy hard-phonon modes are characterized by fluoritelike layers experiencing transverse displacements and large changes in Born effective charges on Bi atoms. Thus, the breaking of symmetry caused by doping of Bi sites within the fluoritelike layer leads to the formation of uncancelled permanent dipole moments along the transverse direction. This provides an opportunity for doping the Bi site in the fluoritelike layer. Isovalent dopants P, As, and Sb were studied. P is found to be most effective in the reorientation of the spontaneous polarization. It leads to a threefold enhancement of the out-of-plane component of polarization and to a commensurate rotation of the spontaneous polarization vector by 36.2° towards the transverse direction. DOI: https://doi.org/10.1103/PhysRevB.99.014101
Dr. Sanjeev Nayak publishes in Scripta Mater. on GP Zone Formation
Dr. Sanjeev Nayak in collaboration with Dr. Rainer Heber and MSE PhD student Cain Hung develop methods to describe GP zone formation in Al-Cu and Al-Ag alloys. Results published in Scripta Mater.
Tulsi Patel Defends PhD Thesis!
Tulsi defended her dissertation on “Hybrid Additive Manufacturing of Ferroelectric Oxides and Aerospace Alloys” last Tuesday, November 20th, 2018. Her work involved integrating functionality into metallic structural components using additive manufacturing. She will begin an NRC Research Associateship at the Air Force Research Laboratory early 2019, researching new ceramic matrix composite systems for high-temperature aerospace applications.
Graphene Supported Single Atom Transition Metal Catalysts
Dr. Sanjubala Sahoo and colleagues have provided insight for the origin of high catalytic activity for graphene-supported single transition metal atoms for activation of methane molecules. The paper entitled “Graphene Supported Single Atom Transition Metal Catalysts for Methane Activation” published in ChemCatChem, Volume 10, page 3229 (2018) co-authored by S. Sahoo, S. L. Suib and S. P. Alpay was a cover feature for the journal.
Yomery Espinal defends her PhD Thesis!
Yomery Espinal wrapped up her PhD work on 8/2/2018. In her thesis entitled “Design and Synthesis of Functional Nanocomposites for Electronic Applications,” Dr. Espinal concentrated on ferroelectric heterostructures and composites. Her work was partially supported by Army Research Labs. Congratulations from the entire group!
Surface phase diagrams of Titanium
Sanjubala Sahoo and colleagues provide an atomistic level understanding for the interaction of titanium with atmospheric molecules such as oxygen, nitrogen and hydrogen as a function of temperature and gas partial pressure. Findings published in Surface Science 677, 18 (2018). Read more here: https://www.sciencedirect.com/science/article/pii/S0039602818301602
Yomery Espinal analyzes resistive switching in PZT films
Yomery Espinal and colleagues at the Army Research Laboratory have studied the dielectric and resistive switching characteristics of lead zirconate titanate thin films. Read more here: https://aip.scitation.org/doi/abs/10.1063/1.5012984
Yomery Espinal and ARL on direct and indirect pyroelectric measurement
Yomery Espinal and colleagues in Army Research Lab investigated both direct and indirect methods to measure pyroelectric behavior in lead zirconate titanate thin films. Their findings were published in the Journal of Applied Physics.
Y. Espinal, S. P. Alpay, M. Howard, B. Hanrahan, ” Dielectric Properties and Resistive Switching Characteristics of Lead Zirconate Titanate/ Hafnia Heterostructures”, J. Appl. Phys. 124 (2018)
Dr. M.T. Kesim et al. Publish on Corrosion of Ag/W Based Contacts
Dr. M.T. Kesim et al. have published their work, “Corrosion, Oxidation, Erosion and Performance of Ag/W-based Circuit Breaker Contacts: A Review” in Corrosion Sciences.
https://www.sciencedirect.com/science/article/pii/S0010938X17304067