Please use this identifier to cite or link to this item: http://lib.jncasr.ac.in:8080/jspui/handle/10572/2218
Title: Origin of the Order-Disorder Transition and the Associated Anomalous Change of Thermopower in AgBiS2 Nanocrystals: A Combined Experimental and Theoretical Study
Authors: Guin, Satya N.
Banerjee, Swastika
Sanyal, Dirtha
Pati, Swapan Kumar
Biswas, Kanishka
Keywords: Chemistry
Sensitized Solar-Cells
Thermoelectric Performance
Conduction
Dynamics
Crystals
Agsbte2
Driven
Snse
Issue Date: 2016
Publisher: American Chemical Society
Citation: Guin, S. N.; Banerjee, S.; Sanyal, D.; Pati, S. K.; Biswas, K., Origin of the Order-Disorder Transition and the Associated Anomalous Change of Thermopower in AgBiS2 Nanocrystals: A Combined Experimental and Theoretical Study. Inorganic Chemistry 2016, 55 (12), 6323-6331 http://dx.doi.org/10.1021/acs.inorgchem.6b00997
Inorganic Chemistry
55
12
Abstract: Bulk AgBiS2 crystallizes in a trigonal crystal structure (space group, P (3) over bar m1) at room temperature, which transforms to a cation disordered rock salt structure (space group, Fm (3) over barm) at similar to 473 K. Surprisingly, at room temperature, a solution-grown nanocrystal of AgBiS2 crystallizes in a metastable Ag/Bi ordered cubic structure, which transforms to a thermodynamically stable disorded cubic structure at 610 K. Moreover, the order-disorder transition in nanocrystalline AgBiS2 is associated with an unusual change in thermopower. Here, we shed light on the origin of a order-disorder phase transition and the associated anomalous change of thermopower in AgBiS2 nanocrystals by using a combined experimental, density functional theory based first-principles calculation and ab initio molecular dynamics simulations. Positron-annilation spectroscopy indicates the presence of higher numbers of Ag vacancies in the nanocrystal compared to that of the bulk cubic counterpart at room temperature. Furthermore, temperature-dependent two-detector coincidence Doppler broadening spectroscopy and Doppler broadening of the annihilation radiation (S parameter) indicate that the Ag vacancy concentration increases abruptly during the order disorder transition in nanocrystalline AgBiS2. At high temperature, a Ag atom shuttles between the vacancy and interstitial sites to form a locally disordered cation sublattice in the nanocrystal, which is facilitated by the formation of more Ag vacancies during the phase transition. This process increases the entropy of the system at higher vacancy concentration, which, in turn, results in the unusual rise in thermopower.
Description: Restricted Access
URI: http://hdl.handle.net/10572/2218
ISSN: 0020-1669
Appears in Collections:Research Articles (Swapan Kumar Pati)
Research Papers (Kaniska Biswas)

Files in This Item:
File Description SizeFormat 
89.pdf
  Restricted Access
4.42 MBAdobe PDFView/Open Request a copy


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.