NOVEL MIXED-VALENT TRANSITION METAL OXIDESMas A. Subramanian, Oregon State University, DMR 0804167

• This is an exploratory research project on the identification, synthesis and characterization of new mixed-valent metal oxides with novel functions such as multiferroics. In addition to multiferroic properties (dielectric and magnetic properties), the compounds synthesized under this program are also screened for various phenomena such as superconductivity, magnetoresistance, thermoelectricity, optical properties.

• Earlier we reported the formation of intense blue pigments from Y(In,Mn)O3. Now we have extended this study to discover various other color pigments by replacing Mn3+ with Cu2+, Fe3+ and Ti4+ at trigonal bipyramidal (TBP) sites in hexagonal YMO3 oxide. We conclude that the pigments with any color could be prepared using this chemistry.

• Our exploratory research on mixed valent transition metal oxides led to the discovery of many new compounds with fascinating structures and properties. One example is a new mixed valent copper rhodium oxide, Bi1.4CuORh5O10 with edge-shared RhO6 octahedra and CuO4 units. The compound is a degenerate semiconductor. Now we are tuning the composition to make it metallic or a superconductor.

The structure of hexagonal YMO3 (left) where M cation sits in TBP. Color pigment samples when M = In, Mn, Cu, Ti, Fe are also shown.

Crystal Structure of Bi1.4CuORh5O10

• This program is providing training for both undergraduate and graduate students in synthetic materials chemistry, crystal structure analysis and electronic properties. This program also provides these students with the intellectual challenge of understanding the complex behavior of newly synthesized materials and help forge links between chemistry, physics and material science.

• The high school portion of the outreach program is being conducted in conjunction with the successful ASE (Apprenticeships in Science and Engineering) portion of the Saturday Academy Program. So far, six high school students participated in this program (2008-11). The ASE organization helped to recruit potential future scientists from regional high schools to participate in this program.

• Students participating in this research program are gaining experience that will prepare them well for the modern academic and industrial environments.

10h Grader Olivia Anderson-Gregg (Philomath High School) testing superconductors she made in PI laboratory during his stay in the summer of 2011. Her mentor was Sean Muir (graduate student).

Our discovery of novel color pigments based on trigonal bipyramidal coordination compounds received world-wide interest and was featured in many press articles/magazines. A recent one from July 29, 2011 Gazette Times newspaper is shown here. Major pigment companies (BASF and Shepherd Color Company) are testing them for various applications under agreement.

NOVEL MIXED-VALENT TRANSITION METAL OXIDESMas A. Subramanian, Oregon State University, DMR 0804167