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Polymorphic Phase Transitions in Nanocrystalline Binary Metal Oxides
Author(s) -
Sood S.,
Gouma P.
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.12124
Subject(s) - nanocrystalline material , materials science , particle size , phase (matter) , orthorhombic crystal system , thermodynamics , particle (ecology) , monoclinic crystal system , anatase , nanomaterials , chemical physics , nanotechnology , crystallography , chemistry , crystal structure , organic chemistry , physics , oceanography , photocatalysis , geology , catalysis
Binary metal oxides occur in different polymorphic states under applied pressure and temperature. Structural changes occur due to polymorphic transitions in binary metal oxides. It is essential to theoretically predict the conditions of polymorphic transitions so that materials can be effectively used in engineering applications. Temperature and pressure are the two main factors affecting the bulk state phase transformation of materials. For nanomaterials, it has been observed that particle size and temperature are the main factors affecting the phase transformation, e.g., γ‐ Fe 2 O 3 to α‐ Fe 2 O 3 , monoclinic to orthorhombic transformation in MoO 3 , anatase to rutile transformation in Titania, γ to α Alumina transformation. We compile from literature the main factors which affect the phase stability of a nanocrystalline binary metal oxide. A heuristic approach to formulate particle size is put forth. Factors like surface energy, surface tension, and particle shape are considered, and a value for critical particle size is formulated. The model fits well with the experimental results for nanocrystalline alumina, titania, zirconia, and Fe 2 O 3 . Such an approach can be applied to predict the particle size‐dependent stability of a phase at known temperature range.