High-pressure synthesis and crystal growth of the polar metal LiOsO3

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PART I: NON-TECHNICAL SUMMARYCrystals are the basis for many modern technologies. With their high degree of structural perfection and chemically tunable compositions, crystals are at the heart of microelectronics, optics and laser technologies, and photovoltaics. Keeping an edge on the technology of crystal growth for the most advanced materials is a key in US competitiveness in science and technology. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, focuses on the growth of crystals of a newly discovered oxide material that includes the rarely studied element osmium. Large, high-quality crystals are needed in order to fully understand the exotic physical properties of this material and the underlying microscopic interactions. The knowledge gained from the project will benefit the design of new functional materials in sensor technology and photovoltaics. Undergraduate students will work on the project and will also be involved in outreach programs such as Alice in Wonderland for female high school students and the annual Explore UT event for students, parents, and teachers. PART II: TECHNICAL SUMMARYThe ilmenite LiOsO3, first reported in 2013, is a polar metallic solid that is an excellent candidate for examining the interplay between metallic and ferroelectric properties. It is metallic to 0.1 K and undergoes a second order non-polar to polar structural transition at 130 K. The transition to a polar structure changes the electronic behavior dramatically, but mobile electrons remain to screen the dipoles from interacting with one another so the polar state is not switchable. How electrons move in the presence of dipoles remains poorly understood. To reveal physical properties reliably, measurements with advanced probes on large, high-quality crystals are necessary, but crystal growth remains a bottleneck in the study of LiOsO3. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, aims to grow high quality, large crystals of LiOsO3 by using high-temperature and high-pressure conditions. The crystal growth will be enhanced by (1) mapping the growth conditions in the pressure-temperature phase diagram and (2) optimal selection of the starting materials and flux. Crystal quality will be checked by Laue back reflection and X-ray diffraction rocking-curve scans. Crystals grown in this project will be not only studied in the PI's lab, but also provided to other research laboratories with advanced characterization facilities but lacking the means for crystal growth under high pressure, which will contribute to the broader impacts of the research. Undergraduate students will work on the project and will also be involved in outreach programs such as Alice in Wonderland for female high school students and the annual Explore UT event for students, parents, and teachers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.