Structural transformations and phenomenological description of the formation of phase states in elpasolites Cs2RbDyF6 and Rb2KB′F6 (B′ = Ho, Dy, Tb)

Сафонов, Иван Н.; Misyul, S. V.; Мolokeev, Maxim S.; Ivliev, M. P.

doi:10.1134/s1063783415030282

Cited by 4 publications

(4 citation statements)

References 7 publications

(11 reference statements)

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“…Chapter 9 -Temperature phase transitions in Rb2KRe3 + F6 elpasolites monoclinic structure, as it was noted in [22].…”

Section: Iv1 Low-frequency Lattice Modesmentioning

confidence: 86%

“…Rb ions are located in (8c) positions that make their vibrations Raman active in contrast to perovskite cubic lattices. It should be pointed that K-F bonds are rather weak and KF6 octahedra are mostly a figure of imagination, while ReF6 are quite rigid complex ions, and their typical frequencies of internal vibrations are well known and given in many textbooks like The cooling results in the first phase transition into the tetragonal phase [22,23] (Fig. 1b).…”

Section: I1 Structure Symmetry Phase Transitionsmentioning

confidence: 99%

“…2). Transition temperatures for the crystals investigated here, according to [22,28] are given in Table 1.…”

Section: I1 Structure Symmetry Phase Transitionsmentioning

confidence: 99%

“…Several attempts have been performed to find such restoring modes in optical spectra [11,21], but in vain. To explain it, other mechanisms of the cubic phase instability have been proposed, like strong anharmonism of CF6 rotations, cluster model [7], or ordering of these groups under cooling [11,22,23], but they disagree with calorimetric data [24].…”

Section: Introductionmentioning

confidence: 99%

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Temperature phase transitions in Rb2KRe3+F6 elpasolites - Raman spectroscopy study

et al. 2021

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Phase transitions in crystals of fluorine-containing elpasolites are investigated by Raman scattering spectroscopy. It was found that lattice instabilities in these crystals are induced by soft mode condensations, while restorations of these modes in the distorted phases have not been observed due to their strong interactions with low-frequency noncritical lattice vibrations. Increasing the mass of a rare-earth ions shifts down frequencies of noncritical modes, that enhances these interactions and leads to a narrowing of the range of existence of intermediate phase and then to its disappearance.

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“…Chapter 9 -Temperature phase transitions in Rb2KRe3 + F6 elpasolites monoclinic structure, as it was noted in [22].…”

Section: Iv1 Low-frequency Lattice Modesmentioning

confidence: 86%

Section: I1 Structure Symmetry Phase Transitionsmentioning

confidence: 99%

“…2). Transition temperatures for the crystals investigated here, according to [22,28] are given in Table 1.…”

Section: I1 Structure Symmetry Phase Transitionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temperature phase transitions in Rb2KRe3+F6 elpasolites - Raman spectroscopy study

et al. 2021

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Why are Double Perovskite Iodides so Rare?

2021

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Following on the heels of the remarkable lead halide perovskite optoelectronic materials, interest in lead-free halide perovskites has grown rapidly in the past decade. Double perovskite halides with the general formula A 2 M I M III X 6 (where A is a large monovalent cation in the perovskite A site, M I is a univalent metal, M III is a trivalent metal, and X = halide) represent one of the promising classes of such materials and, of these, the iodides are particularly interesting since their band gaps are expected to be similar to those found in the iconic lead-containing phases, APbI 3 . However, the successful synthesis of A 2 M I M III I 6 iodides appears to have been elusive. In this work, we examine the likelihood that double perovskite halides will form, using a combination of the Goldschmidt tolerance factor and the radius ratio of the trivalent metals, M III , and rationalize the rarity of double perovskite iodides in terms of these descriptors. Using this model as the formability criterion, we predict the possible existence of more than 300 hitherto unknown double perovskite iodides with organic and inorganic cations in the A site. AUTHOR INFORMATION

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