skip to main content

SciTech ConnectSciTech Connect

Title: Al insertion and additive effects on the thermoelectric properties of yttrium boride

The aluminoboride Y{sub x}Al{sub y}B{sub 14} (x ∼ 0.57, 0.41 ≤ y ≤ 0.63) has been found to show striking p-n control of the thermoelectric properties through variations of the y occupancy of the Al site. The effect of Al was investigated in further extremes. Polycrystalline samples of Al-free Y{sub x}B{sub 14}(x ∼ 0.55; “YB{sub 25}”) were successfully synthesized in sufficient amounts for bulk spark plasma sintering (SPS) samples and their thermoelectric properties were investigated. Y{sub 0.56}Al{sub 0.57}B{sub 14} was also prepared in comparison, and further Al was added to the samples through SPS treatment. We observed that Y{sub 0.55}B{sub 14} exhibits large positive Seebeck coefficients, ∼1000 μV K{sup −1}, around room temperature and the absolute value of the Seebeck coefficient largely decreases with increase of temperature while that of Y{sub 0.56}Al{sub 0.57}B{sub 14} is proportional to T{sup −1/2}, indicating a strong effect of Al on the electronic structure around the Fermi level. Y{sub 0.55}B{sub 14} was found to be strongly disordered with a relatively low thermal conductivity and short localization length of 0.65 Å which is close to that previously determined for the disordered and thermally glass-like compound YB{sub 66}. Occupancy of Al could not be increased further for the Al-rich sample, although Al wasmore » discovered to act as a sintering aid to enhance density and ZT could be significantly improved by 50%.« less
Authors:
 [1] ;  [2] ;  [1] ; ; ;  [3] ;  [1] ;  [2]
  1. National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan)
  2. (Japan)
  3. Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)
Publication Date:
OSTI Identifier:
22271178
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 12; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINIUM BORIDES; COMPARATIVE EVALUATIONS; ELECTRONIC STRUCTURE; FERMI LEVEL; POLYCRYSTALS; SEEBECK EFFECT; SINTERING; TEMPERATURE RANGE 0273-0400 K; THERMAL CONDUCTIVITY; THERMOELECTRIC PROPERTIES; YTTRIUM BORIDES