Empirical models for layered A‐site ordering in perovskite titanates. Issue 5 (5th November 2018)

• Record Type: Journal Article
• Authors: Smith, Evan; Ubic, Rick
• Is Part Of: Journal of the American Ceramic Society. Volume 102:Issue 5(2019)
• Page Start: 3019
• Page End: 3031
• Publication Date: 2018-11-05
• Subjects: electroceramics -- modeling/model -- perovskites -- titanates -- vacancies; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.16168
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: In industry and labs, predictive models describing processing‐structure relationships are inherently valuable, yet few exist for cation ordering in perovskites. In this work, 15 compositions in the [(Na y Li1− y )(1−3 x )/2 La(1+ x )/2 ]TiO3 (NLLT) system ( y = 0.25, 0.5, and 0.75; x = 0, 0.0533, 0.1, 0.1733, and 0.225) were synthesized using a conventional solid‐state mixed‐oxide method. X‐ray diffraction data show that some degree of long‐range ordering of A‐site cations exists for x ≥ 0.1, although electron‐diffraction data indicate that short‐range ordering exists even for x < 0.1, with the degree of ordering decreasing as the value of x increases. Empirical models have been derived for the A‐site ordering parameter (η) as well as the resultant expansion (Δ r A ) for each y series in the NLLT system, from which two general models were derived for perovskites with any arbitrary degree of 1:1 layered A‐site ordering. These general models allow for the prediction of the order parameter and resulting expansion using only published ionic radii data. Abstract : A‐site size adjustment factors as functions of composition from experimentally collected data for (Na y Li1− y )(1−3 x )/2 La(1+ x )/2 TiO3 and A‐site order parameter, η, as a function of composition. The y = 0 data are from Ref. 7.