Morphology control of nanostructures: Na-doped PbTe-PbS system

Jiaqing He*, I. D. Blum, Hui Qiong Wang, S. N. Girard, J. Doak, Li Dong Zhao, Jin Cheng Zheng, G. Casillas, Christopher M Wolverton, M. Jose-Yacaman, David N Seidman, Mercouri Kanatzidis, Vinayak P Dravid

*Corresponding author for this work

Research output: Contribution to journalArticle

80 Scopus citations

Abstract

The morphology of crystalline precipitates in a solid-state matrix is governed by complex but tractable energetic considerations driven largely by volume strain energy minimization and anisotropy of interfacial energies. Spherical precipitate morphologies are favored by isotropic systems, while anisotropic interfacial energies give energetic preference to certain crystallographically oriented interfaces, resulting in a faceted precipitate morphology. In conventional solid-solution precipitation, a precipitate's morphological evolution is mediated by surface anchoring of capping molecules, which dramatically alter the surface energy in an anisotropic manner, thereby providing exquisite morphology control during crystal growth. Herein, we present experimental evidence and theoretical validation for the role of a ternary element (Na) in controlling the morphology of nanoscale PbS crystals nucleating in a PbTe matrix, an important bulk thermoelectric system. The PbS nanostructures formed by phase separation from a PbI2-doped or undoped PbTe matrix have irregular morphologies. However, replacing the iodine dopant with Na (1-2 mol %) alters dramatically the morphology of the PbS precipitates. Segregation of Na at PbTe/PbS interfaces result in cuboidal and truncated cuboidal morphologies for PbS. Using analytical scanning/transmission electron microscopy and atom-probe tomography, we demonstrate unambiguously that Na partitions to the precipitates and segregates at the matrix/precipitate interfaces, inducing morphological anisotropy of PbS precipitates. First-principles and semiclassical calculations reveal that Na as a solute in PbTe has a higher energy than in PbS and that Na segregation at a (100) PbTe/PbS interface decreases the total energy of matrix/precipitate system, resulting in faceting of PbS precipitates. These results provide an impetus for a new strategy for controlling morphological evolution in matrix/precipitate systems, mediated by solute partitioning of ternary additions.

Original languageEnglish (US)
Pages (from-to)5979-5984
Number of pages6
JournalNano Letters
Volume12
Issue number11
DOIs
StatePublished - Nov 14 2012

Keywords

  • Nanostructures
  • morphology control
  • thermoelectric materials
  • transmission electron microscopy

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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    He, J., Blum, I. D., Wang, H. Q., Girard, S. N., Doak, J., Zhao, L. D., Zheng, J. C., Casillas, G., Wolverton, C. M., Jose-Yacaman, M., Seidman, D. N., Kanatzidis, M., & Dravid, V. P. (2012). Morphology control of nanostructures: Na-doped PbTe-PbS system. Nano Letters, 12(11), 5979-5984. https://doi.org/10.1021/nl303449x