Tolerance factor as the basic criterion in searching for promising oxygen-ion and proton conductors among Ln2-xDxM2O7-δ (Ln = La-Lu; M= Sn, Ti, Zr, Hf; D= Sr, Ca, Mg; x = 0, 0.1) 3+/4+ pyrochlores. (August 2019)

• Record Type: Journal Article
• Authors: Shlyakhtina, A.V.; Pigalskiy, K.S.
• Is Part Of: Materials research bulletin. Volume 116(2019)
• Page Start: 72
• Page End: 78
• Publication Date: 2019-08
• Subjects: Pyrochlores -- Order to disorder phase transformations -- Superionic conductivity -- Vacancies -- Tolerance factor; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2019.04.021
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: 800 °C oxygen- ion conductivity as a function of tolerance factor for Ln2-xDxM2O7-δ (Ln = La- Lu; M = Ti, Zr, Hf; D = Sr, Ca, Mg; x = 0, 0.1). The circles, triangles, rhombi, and asterisks represent rare-earth zirconates, hafnates, titanates, and stannates, respectively. The filled and open data points refer to undoped and doped compounds, respectively. The dashed lines illustrate the trends revealed for the (1) titanates, (2) zirconates, and (3) hafnates. The dot-dashed lines indicate the boundaries of the pyrochlore phase field. Highlights: Ln2-x Dx M2 O7- δ (Ln = RE; M = Ti, Zr, Hf; D = Sr, Ca, Mg; x = 0, 0.1) pyrochlores. Geometric parameter characterizing the pyrochlore structure (tolerance factor G). Maximum conductivity near the pyrochlore-fluorite phase boundary (pb). Maximum conductivity near the pyrochlore - perovskite-related monoclinic pb. Tolerance factor G is a good criterion that allows high conductors to be predicted. Abstract: A criterion has been proposed for searching for promising solid oxide fuel cell materials among Ln2-x Dx M2 O7-δ (Ln = La-Lu; M = Ti, Zr, Hf; D = Sr, Ca, Mg; x = 0, 0.1) pyrochlores using a geometric parameter characterizing the pyrochlore structure (tolerance factor G). Analysis of a large amount of experimental oxygen ion and proton conductivity data has made it possible to identify general trends in the behavior of the transport properties of both undoped and doped rare-earth pyrochlores. In the case of the rare-earth titanate, zirconate, and hafnate pyrochlores, the tolerance factor G has been shown to be a good criterion that allows highly conductive compounds to be predicted.