Abstract
Heat and charge transport properties of the metallic unconventional clathrate BaNi2P4, hosting Ba cations in oversized Ni8P16 cages, are investigated. A novel method of single-crystal growth was developed, yielding 2-3 mm sized crystals of BaNi2P4. We also developed a setup to accurately measure thermal conductivity and electrical resistivity of the synthesized single crystals in a wide temperature range avoiding crystal remounting. BaNi2P4 has a metallic temperature dependence of its electrical resistivity (decreasing with decreasing temperature) and manifests an unconventional T2 power law for 50 K < T < 300 K; below 50 K, the power-law exponent increases gradually such that below 10 K the power law is T5, a predicted but extremely rarely experimentally observed dependence for peculiar electron-phonon interactions. Electronic band structure calculations, consistent with measurements of de Haas-van Alphen oscillations, show large band dispersions with significant contributions of Ba orbitals to states near the Fermi level, which is atypical for clathrates. The thermal properties of BaNi2P4 were probed using a combination of variable-temperature single-crystal X-ray diffraction experiments, heat capacity measurements, first-principles phonon dispersion calculations, and inelastic neutron scattering measurements. BaNi2P4 exhibits significant hybridization of the Ba-guest and Ni-P-framework vibrational modes, which may be enhanced via the detected split of the Ba position, which results in strong Ba-framework interactions.
| Original language | English |
|---|---|
| Pages (from-to) | 7932-7940 |
| Number of pages | 9 |
| Journal | Chemistry of Materials |
| Volume | 32 |
| Issue number | 18 |
| DOIs | |
| State | Published - Sep 22 2020 |
Funding
This research was primarily supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering. Synthesis, crystal growth, and structural analysis as well as preliminary PPMS-based properties measurements by J.W., J.-A.D., and K.K. were supported under Award DE-SC0008931. Resistivity and thermal conductivity measurements by E.H.K., E.T., M.A.T., and R.P., Laue diffraction studies by D.L.S., band structure calculations by L.-L.W., heat capacity studies by U.S.K., magnetization measurements by S.L.B., as well as careful analysis of the transport data by P.C.C., were performed at Ames Laboratory, which is operated for the U.S. DOE by Iowa State University under contract #DE-AC02-07CH11358. Neutron scattering measurements by J.L.N. and O.D. were supported by the S3TEC EFRC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0001299. Raman measurements by T.L.-A. were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0019299. J.-A.D. acknowledges the DOE-SCGSR fellowship for time spent at Oak Ridge National Laboratory. This research used resources at the Spallation Neutron Source operated by the Oak Ridge National Laboratory, which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The computing resources were made available through the VirtuES project, funded by the Laboratory Directed Research and Development (LDRD) program at ORNL.
| Funders | Funder number |
|---|---|
| DOE-SCGSR | |
| S3TEC EFRC | |
| Scientific User Facilities Division | |
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | DE-SC0019299, DE-SC0001299 |
| Oak Ridge National Laboratory | |
| Laboratory Directed Research and Development | |
| Division of Materials Sciences and Engineering |