Viktor Poltavets
Assistant Professor Office: 433 Chemsitry
Phone: 517-355-9718 388 /
Websites: Research Group - Area
Awards & Honors
Inorganic Materials Chemistry: Energy Materials
(Research Description PDF - 1280 kb)Our research projects are directed at the rational design of novel energy related materials, such as new battery, thermoelectric and strongly correlated electron materials.
The area of potentially greatest improvement of the battery materials is the cathode. Materials with layered structures, such as LiCoO2, LiNi0.80Co0.15Al0.05O2 and their variants suffer from thermal instability on delithiation, which compromises the safety of Li-ion cells. In our lab we synthesize new transitional metal compounds with framework or layered structures and establish their crystal structures and electrochemical performance.
A new physical mechanism, spin-entropy transport, has been recently identified as a source of enhanced thermopower in layered cobaltates. The spin-entropy thermopower enhancement may be widespread in transition-metal oxides. Design of new transition-metal (Fe, Ti, V, Cr, Mn, Rh) oxide thermoelectric materials with the spin-entropy transport mechanism is the objective of the second research area.
An important class of solid state energy materials is that with so called strong electron correlations. In lower dimensions, the electrons are forced into much stronger interactions with each other. Such strong correlations between electrons are related to many unique properties, such as: high temperature superconductivity, multiferroic, thermoelectric, heavy fermion metallic behavior, and colossal magnetoresistance.
Density functional theory is commonly used to calculate the electronic structure of complex systems. In our group theoretical calculations are used to calculate electronic band structures, Fermi surfaces and total energies of magnetically ordered states. This allows deeper understanding of measured properties. Theoretical properties predictions are also used to identify phases of interest for further synthesis.
The design of advanced materials assumes an understanding of the correlation between chemical composition, crystal structure, crystallite size and shape, and physical/chemical properties. Although it is not possible yet to reliably predict materials properties, there are often crystal structure motives, special features in band structures or in atom spin states which are favorable for a property to emerge. Therefore, the ability to design rationally new compounds is crucial for discovery of materials with advanced properties. Traditional solid state synthetic techniques result in thermodynamically stable phases, which confine our ability to control the final product. One of the rational-design approaches is that of chimie douce, or soft chemistry, which involves low-temperature reactions to form new metastable phases with unique structural features. Using this approach, we design a sequence of low-temperature reactions that will modify the structure in a stepwise process to yield a target product phase.
While doing this research in our group, students are trained in the areas of inorganic synthesis, electrochemistry, crystallography, magnetism, and various characterization techniques. Expertise in synthetic methods and characterization techniques will allow the students to become versatile scientists, well equipped with the technical prerequisites necessary for future independent creative research.
Selected Publications
Electronic Properties, Band Structure, and Fermi Surface Instabilities of Ni1+/Ni2+ Nickelate La3Ni2O6, Isoelectronic with Superconducting Cuprates, V.V. Poltavets, G.H. Fecher, C. Felser, M. Greenblatt, Phys. Rev. Lett. 2009, 102, 046405.Crystal Structures of Ln4Ni3O8 (Ln = La, Nd) T?-type Nickelates, V.V. Poltavets, K.A. Lokshin, M. Croft, T.K. Mandal, T.Egami, M. Greenblatt, Inorg. Chem. 2007, 46, 10887- 10891.
La3Ni2O6: A New T?-type Nickelate with Infinite Ni1+/2+O2 Layers, V.V. Poltavets, K.A. Lokshin, S. Dikmen, M. Croft, T. Egami, M. Greenblatt, J. Am. Chem. Soc. 2006, 128, 90509051.
Charge Transfer, Hybridization and Local Inhomogeneity Effects in NaxCoO2?yH2O: an X-ray Absorption Spectroscopy Study, V.V. Poltavets, M. Croft, M. Greenblatt, Phys. Rev. B 2006, 74, 125103.
Syntheses and Structures of BaPrxBi1-xO3 Perovskites, V. Poltavets, P. Kazin, M. Jansen, Solid State Sciences 2006, 8, 1152- 1159.
