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Research Interests Research efforts in our group are devoted to synthesis, synthetic methodology, and characterization of solid-state inorganic materials with the goal to discover new materials with interesting physical properties and significantly useful technological applications. Of particular interest are materials with promising thermoelectric, photovoltaic and magnetic properties. Areas of research in our group extend from exploratory synthesis and characterization of new inorganic compounds to the development of new methodologies for targeted synthesis and optimization of the properties of both new and existing inorganic materials. Current topics of interest include: nanostructured thermoelectric materials for energy conversion, transition metal chalcogenides and chalcogenide halides combining magnetic and semiconducting properties and new magnetic intermetallic compounds. Nanostructured Thermoelectric Materials In this project, several strategies will be employed to improve the performance of promising thermoelectric materials. We are specifically interested in bulk thermoelectric materials containing nanometer scale inclusions. These materials can achieve significantly enhanced thermoelectric figure of merit (ZT*) over their bulk nanostructure “free” counterparts because of the quantum effects due to electronic confinements that may result in thermopower enhancement. More importantly, lower lattice thermal conductivity is expected because of the contribution of the nano-inclusions to phonons scattering. Thermoelectric materials find uses in variety of application fields ranging from small scale refrigeration (coolers, air conditioners) to power generation (Radioisotope Thermoelectric Generators (RTGs) used in spacecraft). *ZT = sS2T/(kph+kel) where s = electrical conductivity; S = thermopower, kph = lattice thermal conductivity, kel = electronic thermal conductivity and T = absolute temperature Transition Metal ChalcogenidesThe exploration of new systems can ultimately lead to new phases with new structure types and interesting physical properties. We are mostly interested in new quaternary compounds that may combine both semiconducting and magnetic properties. Our strategy is based on careful combination of elements by taking into account the desirable property of the existing binary and ternary phases of those elements. We use several synthetic approaches (high-temperature direct combination, synthesis from fluxes and melts, hydrothermal synthesis, and synthesis from solutions) to coerce elements to react. For example the silver position in the structure of AgBiSCl2 (below) can be substituted isomorphically by other magnetic-bearing transition elements such as Mn, Fe, Co and Ni to build a layer of magnetic elements (M) alternating with along b with a semiconducting layer (SC). Such compounds, when properly optimized can be good candidate materials for spintronics. Our group is part of the Advanced Materials Research Institute (AMRI), a multidisciplinary materials institute that combines the interests of academic, government and industrial scientits (www.amri.uno.edu).
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Selected Publications "Nanostructures versus Solid Solutions: Low Lattice Thermal Conductivity and Enhanced Thermoelectric Figure of Merit in Pb9.6Sb0.2Te10-xSex Bulk Materials" P. F. P. Poudeu, J. D’Angelo, H. Kong, A. Downey, J. L. Short, R. Pcionek, T. P. Hogan, C. Uher, M. G. Kanatzidis, J. Am. Chem. Soc. 128, 14347 – 14355, (2006) "The Intergrowth Structure of Ag1.2Bi17.6S23Cl8 and its Relation to the Tubular Structure of Bi6+dS6+3dCl6-3d and the Pavonite Homologue Ag3xBi5–3xS8–6xCl6x–1" P. F. P. Poudeu, M. Ruck J. Solid State Chem, 179, 3640 – 3648 (2006) (Cover Article) "High Thermoelectric Figure of Merit and Nanostructuring in Bulk p-type Na1-xPbmSbyTem+2" P. F. P. Poudeu, J. D’Angelo, A. D. Downey, J. L. Short, T. P. Hogan, M. G. Kanatzidis, Angew. Chem., Int. Ed, 45, 3835 – 3839 (2006) "Design in solid state chemistry based on phase homologies. Sb4Te3 and Sb8Te9 as new members of the series (Sb2Te3)m·(Sb2)n" P. F. P. Poudeu, M. G. Kanatzidis Chem. Commun. , 151, 2672 (2005) "Ag3.5Bi7.5S13, a new member of the homologous series [Bi2S3]2.[AgBiS2](N−1)/2 with N = 8" P. F. P. Poudeu, M. Ruck Acta Cryst , C61, i41 – i43 (2005) "Homologous Silver Bismuth Chalcogenide Halides (N, x)P. I. Syntheses and Crystal Structures of the (0,1)P Compound AgBi2S2Cl3 and Three Members of the(1, x)P Solid Solution Series Ag2xBi4-2xS6-4xBr4x" P. F. P. Poudeu, T. Söhnel, M. Ruck, Z. Anorg. Allg. Chem. , 630 , 1276 (2004) "Synthese, Kristallstruktur und elektronische Bandstruktur der isotypen Sulfidchloride CuBiSCl2 und AgBiSCl2" M. Ruck, P. F. P. Poudeu, T. Söhnel, Z. Anorg. Allg. Chem., 630, 63 (2004) |
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