TY - JOUR
T1 - The Nanocrystalline SnO2-TiO2 System Part II
T2 - Surface Energies and Thermodynamic Stability
AU - Miagava, Joice
AU - Da Silva, Andre L.
AU - Navrotsky, Alexandra
AU - Castro, Ricardo H.R.
AU - Gouvêa, Douglas
N1 - Funding Information:
RHRC thanks the National Science Foundation (NSF), DMR Ceramics 1055504 for financial support. DG and JM thank the CNPq (202226/2011-5) and CAPES for financial support. Calorimetric studies were supported by the U.S. Dept. of Energy, Office of Basic Energy Sciences, grant DE-FG02-03ER46053.
Publisher Copyright:
© 2015 The American Ceramic Society.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - The thermodynamic stability of nanocrystalline SnO2-TiO2 solid solutions was studied experimentally. Microcalorimetry of water adsorption revealed a systematic decrease in the surface energy with increasing Ti4+ content in the SnO2-rich compositions, consistent with previous reports of Ti4+ segregation on the surface. The surface energy change was accompanied by an increase in the magnitude of the heat of water adsorption, also indicating a modification of the SnO2 surface by Ti4+. Supporting the water adsorption data, calculations using high-temperature oxide melt solution calorimetry data also suggest a decrease in the interface energies. A thermodynamic analysis showed that the observed surface energy decrease is responsible for an increase in the stability of solid solutions in the nanophase regime. Although a miscibility gap is expected in this system from bulk phase diagrams, the surface energy contribution modifies the bulk trend and promotes extensive solid solutions when the surface area is above a critical value dependent on the surface energy and the bulk enthalpy of mixing.
AB - The thermodynamic stability of nanocrystalline SnO2-TiO2 solid solutions was studied experimentally. Microcalorimetry of water adsorption revealed a systematic decrease in the surface energy with increasing Ti4+ content in the SnO2-rich compositions, consistent with previous reports of Ti4+ segregation on the surface. The surface energy change was accompanied by an increase in the magnitude of the heat of water adsorption, also indicating a modification of the SnO2 surface by Ti4+. Supporting the water adsorption data, calculations using high-temperature oxide melt solution calorimetry data also suggest a decrease in the interface energies. A thermodynamic analysis showed that the observed surface energy decrease is responsible for an increase in the stability of solid solutions in the nanophase regime. Although a miscibility gap is expected in this system from bulk phase diagrams, the surface energy contribution modifies the bulk trend and promotes extensive solid solutions when the surface area is above a critical value dependent on the surface energy and the bulk enthalpy of mixing.
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U2 - 10.1111/jace.13954
DO - 10.1111/jace.13954
M3 - Article
AN - SCOPUS:84951127426
SN - 0002-7820
VL - 99
SP - 638
EP - 644
JO - Journal of the American Ceramic Society
JF - Journal of the American Ceramic Society
IS - 2
ER -