Combinatorial search of structural transitions: Systematic investigation of morphotropic phase boundaries in chemically
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Combinatorial search of structural transitions: Systematic investigation of morphotropic phase boundaries in chemically substituted BiFeO3 Daisuke Kana) Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742; and Institute for Chemical Research, Kyoto University, Kyoto 611-0011, Japan
Christian J. Long Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742
Christian Steinmetz and Samuel E. Lofland Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey 08028
Ichiro Takeuchi Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (Received 23 July 2012; accepted 30 August 2012)
We review our work on combinatorial search and investigation of morphotropic phase boundaries (MPBs) in chemically substituted BiFeO3 (BFO). Utilizing the thin-film composition spread technique, we discovered that rare-earth (RE 5 Sm, Gd, and Dy) substitution into the A-site of the BFO lattice results in a structural phase transition from the rhombohedral to the orthorhombic phase. At the structural boundary, both the piezoelectric coefficient and the dielectric constant are substantially enhanced. It is also found that the observed MPB behavior can be universally described by the average A-site ionic radius as a critical parameter, indicating that chemical pressure effect due to substitution is the primary cause for the MPB behavior in RE-substituted BFO. Our combinatorial investigations were further extended to the A- and B-site cosubstituted BFO in the pseudoternary composition spread of (Bi1 xSmx)(Fe1 yScy)O3. Clustering analysis of structural and ferroelectric property data of the fabricated pseudoternary composition spread reveals close correlations between the structural and ferroelectric properties. We show that the evolution in structural and ferroelectric properties is controlled solely by the A-site Sm substitution and not the B-site Sc substitution. I. INTRODUCTION 1,2
The combinatorial approach in materials science, in which a large compositional landscape is rapidly mapped and screened for desired physical properties, is an effective way to accelerate the traditional time-consuming and serendipitous trial-and-error processes that we rely on for discovering and developing novel high-performance materials. Owing to recent developments in atomic-scale thin-film fabrication and characterization techniques for inorganic materials, various types of sophisticated combinatorial library designs such as the continuous composition gradients are available not only for identifying materials with desired properties but also for systematically tracking the details of the structure–property relationships of targeted materials.3 6 a)
Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2012.314 J. Mater. Res., Vol. 27, No. 21, Nov 14, 2012
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