P. Shiv Halasyamani
Department of Chemistry
Office: SR1, 53
Contact: firstname.lastname@example.org - 713-743-7716
Education: Ph.D., Northwestern University, 1996; B.S., University of Chicago, 1992
Postdoctoral Fellow, Oxford University, 1997-1998
esearch in the Halasyamani group involves the synthesis, characterization, and development of structure-property relationships in new functional inorganic materials. Functionalities we are interested in include second-order non-linear optical behavior, i.e. second-harmonic generation, piezoelectricity, ferroelectricity, pyroelectricity, and multi-ferroic behavior. In addition to bulk phase synthesis, we also have research programs in large single crystal growth. We utilize a range of diffraction (powder and single crystal X-ray) and non-diffraction (TG/DSC, powder SHG, pyroelectric, etc.) measurements to characterize the materials.
A broad area that we are investigating involves the synthesis, characterization, and structure-property relationships in new polar oxides. Polar materials, those that exhibit a macroscopic dipole moment, exhibit a host of technologically important properties including piezoelectricity, ferroelectricity, and pyroelectricity. We have demonstrated that the incidence of polarity in any new oxide material can be increased by incorporating second-order Jahn-Teller (SOJT) disorted cations. With respect to crystal chemistry, SOJT distortions are observed in oxide environments of octahedrally coordinated d0 transition metals, e.g. Ti4+, Nb5+, and W6+ and cations with non-bonded electron pairs, e.g. Sn2+, Sb3+, and Te4+. We have exploited this distortion and have successfully synthesized a variety of polar materials. We characterize the materials through second-order non-linear optical, i.e. SHG, measurements as well as piezoelectric and polarization measurements. Our recent work has incorporated theoretical calculations to better understand the energetic of polarization reversal.
Another area of research we are investigating involves large single crystal growth – crystals centimeter size or larger. Large single crystals are crucial for detailed physical property measurements that can provide a far better understanding of structure-property relationships. We use a top-seeded solution growth (tssg) technique to grow centimeter size crystals of our functional materials. Currently, we have eight (8) tssg crystal growth furnaces with a maximum temperature of 1200C. This technique has enabled us to grow large crystals of a variety of materials including Na2TeW2O9 and LiFeP2O7 (see Figures above – left and right respectively).
An additional area of research we are involved with concerns multi-ferroic fluorides. For our purposes, multi-ferroic materials exhibit ferroelectricity, i.e. reversible polarization, and some sort of magnetic ordering. We are investigating magnetic ordering in materials that undergo a ‘non-classic’ ferroelectric mechanism, e.g., BaNiF4 (see Figure). As seen in the Figure, the green octahedra and yellow spheres represent the structure of the ‘up’ polarization of BaNiF4, whereas the gray octahedral and spheres represent the structure of the ‘down’ polarization. The structural re-orientation through the NiF6 octahedral rotations and Ba2+ displacements result in the polarization reversal, switching between ‘up’ and ‘down’, i.e. the ferroelectric behavior. We are investigating a host of mixed-metal fluorides that could undergo this non-classic ferroelectric mechanism and exhibit magnetic ordering.
- 2014 - Roy-Somiya Award: International Solvothermal and Hydrothermal Association
- 2014 - present European Research Council Panelist
- 2014 - present ORNL Neutron Sciences Science Review Committee
- 2013 - present Associate Editor: Inorganic Chemistry
- 2013 - present Peer Review Panel Member - Diamond Light Source UK
- 2013-2015 - Editorial Advisory Board: Chemistry of Materials
- 2012 - Guest Editor: Journal of Solid State Chemistry – Polar Inorganic Materials
- 2011 - Visiting Professor for International Scientists – Chinese Academy of Sciences
- 2010 - Dow Lecturer – University of Minnesota
- 2010 - UH Honors Society Fellow
- 2009 - Excellence in Research Award (UH) - Associate Professor Level
- 2008-present - Adjunct Professor: Xinjiang Technical Institute of Physics and Chemistry – Chinese Academy of Sciences
- 2008 - Guest Editor: Inorganic Chemistry – Functional Inorganic Materials
- 2008-2013 - Associate Editor: Materials Research Bulletin
- 2007-2010 - Editorial Advisory Board: Inorganic Chemistry
- 2004 - Excellence in Research Award (UH) - Assistant Professor Level
- 2003 - ExxonMobil Solid State Faculty Award
- 2002 - Beckman Young Investigator
- 2001 - National Science Foundation CAREER Award