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Thermodynamics of Nanoscale Lead Titanate and Barium Titanate Perovskites
Author(s) -
Costa Gustavo C. C.,
Saradhi Maram Pardha,
Navrotsky Alexandra
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2012.05373.x
Subject(s) - nanocrystalline material , barium titanate , materials science , anhydrous , raman spectroscopy , crystallite , lead titanate , analytical chemistry (journal) , mineralogy , ferroelectricity , crystallography , dielectric , chemistry , nanotechnology , physics , optoelectronics , organic chemistry , optics , metallurgy , chromatography
To explore the surface properties of perovskites with ions of different bond character, the surface and interface enthalpies of nanocrystalline PbTiO 3 and BaTiO 3 perovskites were determined for the first time by a combination of calorimetric, morphological, and structural analyses. PbTiO 3 and BaTiO 3 nanocrystalline samples of varying surface areas and degrees of agglomeration were synthesized by solvothermal and hydrothermal methods, respectively. All synthesized samples were characterized using X ‐ray diffraction and Raman spectroscopy. Interface areas were estimated by comparing the surface areas measured by N 2 adsorption to the crystallite sizes refined from X ‐ray diffraction data. The integrated heats of water vapor adsorption on the surfaces of the nanocrystalline phases are −62 ± 4 kJ/mol for PbTiO 3 , which is less exothermic than the value −72 ± 9 kJ/mol for the isostructural BaTiO 3 , both phases having the same chemisorbed water coverage. Similar behavior is observed for the surface and interface enthalpies. The energies of the hydrous and anhydrous surfaces are 1.97 ± 0.67 J/m 2 and 1.11 ± 0.23 J/m 2 for PbTiO 3 , and 3.69 ± 0.22 J/m 2 and 3.99 ± 0.28 J/m 2 for BaTiO 3 , respectively. The interface energies of the hydrous and anhydrous surfaces are 0.55 ± 0.74 J/m 2 and 0.73 ± 0.27 J/m 2 for PbTiO 3 , and 1.11 ± 0.13 J/m 2 for BaTiO 3 . These observations suggest that PbTiO 3 has lower surface energy and lower affinity for water adsorption on the surface than BaTiO 3 and that surface energy and hydrophilicity of the surface decrease with increasing covalent character of the ions, as was seen previously in comparing TiO 2 and SnO 2 .