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Thermodynamics of Nanoscale Calcium and Strontium Titanate Perovskites
Author(s) -
Sahu Sulata K.,
Maram Pardha S.,
Navrotsky Alexandra
Publication year - 2013
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/jace.12622
Subject(s) - nanocrystalline material , calorimetry , enthalpy , ionic radius , calcium titanate , materials science , analytical chemistry (journal) , chemistry , mineralogy , chemical engineering , thermodynamics , dielectric , nanotechnology , ion , physics , optoelectronics , organic chemistry , chromatography , engineering
The surface enthalpies of nanocrystalline CaTiO 3 and SrTiO 3 perovskites were determined using high‐temperature oxide melt solution calorimetry in conjunction with water adsorption calorimetry. The nanocrystalline samples were synthesized by a hydrothermal method and characterized using powder X‐ray diffraction, FTIR spectroscopy, and Brunauer–Emmett–Teller surface area measurements. The integral heats of water vapor adsorption on the surfaces of nanocrystalline CaTiO 3 and SrTiO 3 are −78.63 ± 4.71 kJ/mol and −69.97 ± 4.43 kJ/mol, respectively. The energies of the hydrous and anhydrous surfaces are 2.49 ± 0.12 J/m 2 and 2.79 ± 0.13 J/m 2 for CaTiO 3 and 2.55 ± 0.15 J/m 2 and 2.85 ± 0.15 J/m 2 for SrTiO 3 , respectively. The stability of the perovskite compounds in this study is discussed according to the lattice energy and tolerance factor approach. The energetics of different perovskites suggest that the formation enthalpy becomes more exothermic and surface energy increases with an increase in ionic radius of the “A” site cation ( Ca , Sr , and Ba ), or with the tolerance factor. PbTiO 3 shows a lower surface energy, weaker water binding, and a less exothermic enthalpy of formation than the alkaline‐earth perovskites.