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Abstract Processing–structure relationships are at the heart of materials science, and predictive tools are essential for modern technological industries insofar as structure dictates intrinsic properties; however, few theoretical models exist for cation‐ordered perovskites. In this work, a combination of data mining and solid‐state synthesis was employed to collect structural data of 1:2 ordered (triple) perovskites. Three compositions within the (Ba1 − xSrx)(Mg1/3Ta2/3)O3system were synthesized using a conventional solid‐state mixed‐oxide method. X‐ray diffraction data showed evidence of long‐range 1:2 B‐site cation ordering for all compositions. Additional data for another 24 1:2 ordered compositions were mined from literature. Correlative models for the deviation in modified tolerance factor (Δt′) were derived for each system, and a general model which is capable of predicting the pseudocubic lattice constants of such perovskites based solely on published ionic‐radii data developed.
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Using resonant energy X-ray diffraction to extract chemical order parameters in ternary semiconductors
II–IV–V 2 materials, ternary analogs to III–V materials, are emerging for their potential applications in devices such as LEDs and solar cells. Controlling cation ordering in II–IV–V 2 materials offers the potential to tune properties at nearly fixed compositions and lattice parameters. While tuning properties at a fixed lattice constant through ordering has the potential to be a powerful tool used in device fabrication, cation ordering also creates challenges with characterization and quantification of ordering. In this work, we investigate two different methods to quantify cation ordering in ZnGeP 2 thin films: a stretching parameter calculated from lattice constants , and an order parameter determined from the cation site occupancies ( S ). We use high resolution X-ray diffraction (HRXRD) to determine and resonant energy X-ray diffraction (REXD) to extract S . REXD is critical to distinguish between elements with similar Z -number ( e.g. Zn and Ge). We found that samples with a corresponding to the ordered chalcopyrite structure had only partially ordered S values. The optical absorption onset for these films occurred at lower energy than expected for fully ordered ZnGeP 2 , indicating that S is a more accurate descriptor of cation order than the stretching parameter. Since disorder is complex and can occur on many length scales, metrics for quantifying disorder should be chosen that most accurately reflect the physical properties of interest.
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- Award ID(s):
- 1729594
- PAR ID:
- 10195508
- Date Published:
- Journal Name:
- Journal of Materials Chemistry C
- Volume:
- 8
- Issue:
- 13
- ISSN:
- 2050-7526
- Page Range / eLocation ID:
- 4350 to 4356
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9TC06699C
