Near edge X-ray absorption fine structure measurements (XANES) and extended x-ray absorption fine structure measurements (EXAFS) of the valence state and coordination of antimony in doped nanocrystalline SnO2

Abstract

Colloids of nanocrystalline tin dioxide containing 9.1 at. % and 16.7 at. % antimony have been prepared by the coprecipitation method. High-resolution transmission electron microscopy (TEM) images show crystalline particles in the 2–6 nm size regime. X-ray powder diffraction patterns of nanocrystalline powders obtained by drying the colloids and heating to 100 °C indicate the same rutile lattice structure known from bulk SnO2. On heating to 500 °C in air, the nanocrystalline powder shows a slight increase in particle size but especially a change in color from yellowish to bluish which is accompanied by the development of n-type conductivity. The coordination of antimony in the SnO2 nanocrystallites has been investigated by extended x-ray absorption fine structure measurements (EXAFS) at the Sb K-edge at 5 K while its valence state was determined by near edge x-ray absorption fine structure measurements (XANES) at the Sb L1 edge. The Sb higher neighbor shell distances in the doped material differ from the corresponding distances in Sb2O3 or Sb2O5 but are identical to those in tin dioxide, indicating that antimony is almost completely incorporated into the tin dioxide lattice despite the high doping level. XANES measurements reveal that a large fraction of SbIII employed during the synthesis is already oxidized to SbV at low temperatures. On the basis of these observations, a two-step model for the formation of n-conductive Sb-doped SnO2 nanocrystals is given and quantitatively discussed with respect to the data.

Advanced SnO2-Based Ceramics: Synthesis, Structure, Properties

“…In the case of higher concentration of antimony embeded in the SnO 2 lattice the most likely the resulted solid solution has the the following composition: Sn 4+ 1-2x Sb 3+ x Sb 5+ x O 2-2 . By EXAFS it has been established that Sb dopants occupy Sn sites in the rutile structure [Chadwick et al,1993;Rockenberger et al, 2000]. XANES measurements showed that the largest fraction of Sb has a valency of 5 + , although 3 + was also observed in nanocrystalline SnO 2 .…”

Resistividade do filme depositado via sol-gel e estado de oxidação do dopante Ce na matriz SnO2

“…A combinação das transições de RE com semicondutores de gap largo, como é o caso do SnO 2 (3,6 eV) [2] leva a uma alta efi ciência na emissão [3,4]. Além disso, SnO 2 apresenta alta refl etividade no infravermelho, transparência de cerca de 90% no visível [5,6], e boa condutividade elétrica, propriedades que tornam este material adequado para várias aplicações tecnológicas, incluindo sensores de gás, células solares, entre outras [6,7]. O íon Ce 3+ apresenta confi guração eletrônica 4f 1 no estado fundamental e 5d 1 no estado excitado.…”

Resistividade do filme depositado via sol-gel e estado de oxidação do dopante Ce na matriz SnO2

“…A combinação das transições de RE com semicondutores de gap largo, como é o caso do SnO 2 (3,6 eV) [2] leva a uma alta eficiência na emissão [3,4]. Além disso, SnO 2 apresenta alta refletividade no infravermelho, transparência de cerca de 90% no visível [5,6], e boa condutividade elétrica, propriedades que tornam este material adequado para várias aplicações tecnológicas, incluindo sensores de gás, células solares, entre outras [6,7]. O íon Ce 3+ apresenta configuração eletrônica 4f 1 no estado fundamental e 5d 1 no estado excitado.…”