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Electronic Properties of Bi 2 O 3 Based Solid Electrolytes
Author(s) -
Shuk P.,
Wiemhöfer H.D.,
Göpel W.
Publication year - 1997
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.199762301140
Subject(s) - band gap , x ray photoelectron spectroscopy , analytical chemistry (journal) , fermi level , materials science , solid solution , semimetal , electrolyte , direct and indirect band gaps , chemistry , crystallography , electron , electrode , physics , nuclear magnetic resonance , quantum mechanics , optoelectronics , chromatography , metallurgy
Bi 2 O 3 based solid electrolytes with partial substitution of Bi by Y, Zr, or Pr were prepared and studied by UV and X‐ray photoelectron spectroscopies (UPS, XPS) as well as electron energy loss spectroscopy (EELS). Changes of the band gap and of the position of the Fermi level in the band gap with respect to the band edges were determined as a function of composition. An increase of the band gap is desirable for Bi 2 O 3 based solid electrolytes in order to decrease the electronic conductivity and enlarge the stability and electrolytic domain of these materials. The band gap increases with Y concentration from E gap = 2.8 eV for Bi 0.75 Y 0.25 O 1.5 to E gap = 3.2 eV for Bi 0.60 Y 0.4 O 1.5 . Dissolving PrO 1.83 in Bi 0.75 Y 0.25 O 1.5 up to a composition (Bi 0.75 Y 0.25 O 1.5 ) 0.98 (PrO 1.83 ) 0.02 yields no change of the band gap, whereas Zr substitution causes an increase by 0.4 eV to a value of E gap = 3.2 eV for (Bi 0.75 Y 0.25 O 1.5 ) 0.9 (ZrO 2 ) 0.1 . The position of the Fermi level was 2.1 eV above the valence band edge for Bi 0.75 Y 0.25 O 1.5 in equilibrium with Fe/ FeO reference contacts slightly increasing to 2.3 eV for Bi 0.60 Y 0.4 O 1.5 . The values were temperature independent in the range 650 K to 900 K. Band tails were observed at the band edges extending into the band gap and indicating the high ionic disorder in the lattice. Additional O1s XPS data are given with regard to the surface oxygen species.