Raman scattering and phase transitions in fluorides with elpasolite structure

Vtyurin, A. N.; Крылов, А. С.; Voronov, V. N.; Krylova, S. N.

doi:10.1080/00150193.2017.1349863

Cited by 6 publications

(5 citation statements)

References 19 publications

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“…Apart from the three Raman modes of the MBr 6 octahedra, the crystal symmetries also allow Raman scattering of low-frequency lattice modes, as was observed in elpasolites. − The absence of such Raman modes in our study could possibly be due to their low frequencies (<50 cm –1 ) that are beyond the range of our instrumental coverage.…”

mentioning

confidence: 65%

Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Puttisong

Moro

Chen

et al. 2020

J. Phys. Chem. Lett.

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We show by electron spin resonance (ESR) and Raman spectroscopies that the crystal phase transition of the lead-free double-perovskite Cs2AgBiBr6 has a profound symmetry-breaking effect on the high spin states of, for example, a transition-metal ion Fe3+ and the vibrational modes. It lifts their degeneracy when the crystal undergoes the cubic-tetragonal phase transition, splitting the six-fold degenerate S = 5/2 state of Fe3+ to three Kramer doublets and the enharmonic breathing mode Tg of the MBr6 octahedra (M = Ag, Bi, Fe) into Eg + Ag. The magnitudes of both spin and Raman line splitting are shown to directly correlate with the strength of the tetragonal strain field. This work, in turn, demonstrates the power of the ESR and Raman spectroscopies in probing structural phase transitions and in providing in-depth information on the interplay between the structural, spin, and vibrational properties of lead-free double perovskites, a newly emerging and promising class of materials for low-cost and high-efficiency photovoltaics and optoelectronics.

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mentioning

confidence: 65%

Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Puttisong

Moro

Chen

et al. 2020

J. Phys. Chem. Lett.

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“…These results are in good correlation with our XRD results. The crystal symmetries also permit Raman scattering of low-frequency lattice modes of Cs 2 AgBiBr 6 DP, as was discovered in elpasolites, in addition to the three characteristic Raman modes of the BBr 6 octahedra. , We have fitted the Raman spectra for all three substrates with a Lorentzian line shape, which reveals the fwhm of A 1g mode as 10.74, 10.23, and 9.80 cm –1 for Si, quartz, and SiO 2 substrates, respectively, suggesting the highly crystalline growth of Cs 2 AgBiBr 6 DP deposited on the SiO 2 substrate. Raman shifts of all of the modes with respective fwhm are tabulated in Table S4.…”

Section: Resultsmentioning

confidence: 99%

Chemical Vapor Deposition Growth of Highly Stable Cs₂AgBiBr₆ Double Perovskite Thin Films and Their Ultralow Thermal Conductivity and Fast Photoresponse

Chahal,

Bora,

Giri

2023

ACS Appl. Energy Mater.

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As an alternative to lead-based perovskites, Cs 2 AgBiBr 6 is an emerging lead-free double perovskite (DP), which has shown promise in the field of optoelectronics owing to its nontoxicity, high stability, and superior photoelectric properties. Herein, we demonstrate the growth of a highly crystalline and uniform Cs 2 AgBiBr 6 thin film via chemical vapor deposition (CVD). By tuning the growth temperature, we successfully obtained Cs 2 AgBiBr 6 thin films of high structural and compositional uniformity, confirmed by XRD, Raman, and XPS studies. Substrate-dependent growth aided the study of the induced lattice strain in the system. Temperature-dependent Raman analysis of the A 1g mode was used to determine the thermal stability of the asgrown film and to estimate the temperature coefficient of the A 1g mode (α ∼ −0.01431 ± 0.0039 cm −1 K −1 ) in the Cs 2 AgBiBr 6 thin film. Power-dependent Raman spectral analysis was employed to evaluate the thermal conductivity of suspended Cs 2 AgBiBr 6 as ∼1.97 ± 0.48 W/m-K. A detailed study of the electron−phonon and phonon−phonon interactions in the Cs 2 AgBiBr 6 DP system was carried out. Additionally, due to its excellent absorption in the UV−vis region and long carrier lifetime, the CVD-grown Cs 2 AgBiBr 6 film on a SiO 2 substrate was utilized as a photodetector. The planar photodetector device, in addition to being selfpowered, exhibited a fast photoresponse of ∼170/177 μs, which is far superior to that of Cs 2 AgBiBr 6 -based photodetectors reported to date. Thus, this work paves the way for the direct CVD growth of highly compact and uniform Cs 2 AgBiBr 6 films on arbitrary substrates with exceptional thermal and environmental stability and superior optoelectronic performance. We believe that our results will eventually provide insightful strategies for developing high-performance optoelectronic devices based on lead-free inorganic double perovskites.

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“…Replacing scandium for heavier rare-earth ions moves these noncritical low-frequency lattice modes down, increases this interaction and as a result, destroys the cubic phase at higher temperatures [8]. A linear deviation of these frequencies from the extrapolated values is seen, that is supposed to be proportional to the order parameter below phase transitions of the second order or the first order close to the tricritical point.…”

Section: Iv1 Low-frequency Lattice Modesmentioning

confidence: 97%

“…The changes of external parameters cause structural phase transitions in these crystals. The temperature phase transitions have been investigated earlier in [7][8][9][10][11][12][13][14][15][16] and phase transitions under hydrostatic pressure as well as P-T phase diagrams in [17,18]; detailed symmetry analysis was proposed in [19]. It should be pointed out that these successions of phase transitions differ considerably from those observed in oxide analogues, that attracts special interest to them.…”

Section: Introductionmentioning

confidence: 99%

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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Raman scattering and phase transitions in fluorides with elpasolite structure

Cited by 6 publications

References 19 publications

Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Chemical Vapor Deposition Growth of Highly Stable Cs₂AgBiBr₆ Double Perovskite Thin Films and Their Ultralow Thermal Conductivity and Fast Photoresponse

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

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Raman scattering and phase transitions in fluorides with elpasolite structure

Cited by 6 publications

References 19 publications

Effect of Crystal Symmetry on the Spin States of Fe3+ and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6

Effect of Crystal Symmetry on the Spin States of Fe3+ and Vibration Modes in Lead-free Double-Perovskite Cs2AgBi(Fe)Br6

Chemical Vapor Deposition Growth of Highly Stable Cs2AgBiBr6 Double Perovskite Thin Films and Their Ultralow Thermal Conductivity and Fast Photoresponse

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

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Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Effect of Crystal Symmetry on the Spin States of Fe³⁺ and Vibration Modes in Lead-free Double-Perovskite Cs₂AgBi(Fe)Br₆

Chemical Vapor Deposition Growth of Highly Stable Cs₂AgBiBr₆ Double Perovskite Thin Films and Their Ultralow Thermal Conductivity and Fast Photoresponse