High-pressure transition to the post-barite phase in BaCrO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>hashemite

Santamarı́a-Pérez, D.; Kumar, Ravhi S.; santos‐García, Antonio J. Dos; Errandonea, Daniel; Chuliá-Jordán, Raquel; Sáez-Puche, R.; Rodríguez‐Hernández, P.; Múñoz, A.

doi:10.1103/physrevb.86.094116

Cited by 27 publications

(22 citation statements)

References 50 publications

(39 reference statements)

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“…As the excitation power is decreased, the intensity of the lower energy band remarkably drops, broadens, and shifts to lower energy, whereas the higher energy band nearly vanishes (see Figure ). Because two coexisting crystallographic phases − in several inorganic perovskite materials of mixed − and pure − composition, including MAPbI 3 , have been already observed, we suggest that the measured emission in the low-temperature phase could be explained by supposing a very small relative volume fraction of low-energy sites attributable to small embodiments of individual tetragonal phase crystallites, where photoexcited carriers can be trapped . Therefore, the subgap sites in the tetragonal crystallites can only be partially filled under weak excitation by the few free carriers.…”

Section: Resultsmentioning

confidence: 71%

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

et al. 2018

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In this work, we have investigated the crystalline-size dependence of optical absorption and photoluminescence emission of CH 3 NH 3 PbI 3 films, which is necessary to identify the potential practical applications of the gadgets based on perovskite films. This study was carried out at low temperatures to minimize the extra complexity induced by thermal effects. The purpose was to clarify the origin of the dual emission peak previously reported in the literature. We found that the grain size is responsible for the appearance or disappearance of this dual emission on CH 3 NH 3 PbI 3 at low temperatures, whereas we have inferred that the thickness of the perovskite layer is a much more important factor than the size of the grains in the location of the energy of the band gap. Moreover, the increase in the grain size allows slowing down the phase transition. Additionally, we evidence a decrease in the effective Rydberg energy of the exciton in several samples, from 23−25 meV at 7 K to 12−13 meV at 165 K, by fitting to Elliott−Toyozawa theory. We have extracted other important physical parameters of perovskites from the photoluminescence-data deconvolution, such as the band gap, exciton−phonon interaction, and exciton binding energy. A new phase transition at 45.5 K was determined by the temperature dependence of full width at half-maximum and the integrated intensity of the photoluminescence, and it was confirmed by the radiative lifetime obtained from the time-resolved photoluminescence emission by means of time-correlated single-photon counting at different temperatures, excitation fluencies, and emission energies.

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Section: Resultsmentioning

confidence: 71%

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

et al. 2018

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“…The pressure-induced phase transition of ABO 4 oxides has been studied extensively for many different crystal structures, such as phase transition from scheelite to fergusonite in molybdates and tungstates, , phase transition from zircon to scheelite in vanadates and chromates. , On the basis of a large number of theoretical works and experiments, a general conclusion was that the radii ratios r A / r O and r B / r O between cation and oxygen increase with pressure, resulting in an increase of cation coordination in the high-pressure modifications. , Most of the zircon structure ABO 4 oxides are known to undergo a phase transition from zircon-type to scheelite-type under pressure. Furthermore, a zircon–monazite–scheelite sequence of stable structure was suggested as a likely pressure-driven route for zircon-type ABO 4 oxides .…”

Section: Resultsmentioning

confidence: 99%

Pressure and Temperature Study on the Structural Stability of GdNbO₄:Eu³⁺

et al. 2017

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Lanthanide niobate is an excellent nonlinear optical and high dielectric constant material. However, development and application of these novel properties depend on an understanding of its structural stability. In this work, Raman and luminescence spectra of GdNbO4 with different Eu3+ ions doping concentrations under high pressure and low temperature were obtained. The evolution of Raman spectra indicated that an irreversible structural phase transition of GdNbO4 from monoclinic phase to M′-fergusonite phase occurred at 6.2 GPa, and the phase transition was completed at about 13.1 GPa. An obvious discontinuity on Eu3+ ions luminescence intensity ratio between the 5D0 → 7F2 and the 5D0 → 7F1 transition lines was observed with increasing pressure. The results indicated that the site symmetry of Eu3+ ions in GdNbO4:Eu3+ was changed, which was in agreement with high-pressure Raman spectra data. Meanwhile, Raman and luminescence spectra showed that the crystal structure remained stable in the temperature range of 20–300 K.

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“…A decade-long effort has been dedicated by several research groups around the world to study the high-pressure (HP) behavior of chromates with formula ACrO 4 . The interest in their HP conduct is many-fold, going from Earth to material sciences. , Several articles have been published reporting structural phase transitions and discussing the influence of compression on the electronic, magnetic, and vibrational properties of these compounds. − In particular, barite-type BaCrO 4 has been studied by means of ab initio calculations, Raman spectroscopy, and powder X-ray diffraction up to 50 GPa. − A phase transition has been reported near 27 GPa, and the crystal structure of the HP phase determined . Interestingly, the existence of two soft-mode phonons has been found in the HP polymorph indicating that it is unstable at pressures higher than those achieved in the experiments .…”

Section: Introductionmentioning

confidence: 99%

High-Pressure Single-Crystal X-ray Diffraction of Lead Chromate: Structural Determination and Reinterpretation of Electronic and Vibrational Properties

et al. 2019

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We have investigated the high-pressure behavior of PbCrO4. In particular, we have probed the existence of structural transitions under high pressure (at 4.5 GPa) by single-crystal X-ray diffraction and density functional theory calculations. The structural sequence of PbCrO4 is different than previously determined. Specifically, we have established that PbCrO4, under pressure, displays a monoclinic–tetragonal phase transition, with no intermediate phases between the low-pressure monoclinic monazite structure (space group P21/n) and the high-pressure tetragonal structure. The crystal structure of the high-pressure polymorph is, for the first time, undoubtedly determined to a tetragonal scheelite-type structure (space group I41/a) with unit-cell parameters a = 5.1102(3) Å and c = 12.213(3) Å. These findings have been used for a reinterpretation of previously published Raman and optical-absorption results. Information of calculated infrared-active phonons will be also provided. In addition, the pressure dependence of the unit-cell parameters, atomic positions, bond distances, and polyhedral coordination are discussed. The softest and stiffest direction of compression for monazite-type PbCrO4 are also reported. Finally, the theoretical pressure dependence of infrared-active modes is given, for the first time, for both polymorphs.

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High-pressure transition to the post-barite phase in BaCrO4hashemite

Cited by 27 publications

References 50 publications

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

Pressure and Temperature Study on the Structural Stability of GdNbO₄:Eu³⁺

High-Pressure Single-Crystal X-ray Diffraction of Lead Chromate: Structural Determination and Reinterpretation of Electronic and Vibrational Properties

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High-pressure transition to the post-barite phase in BaCrO4hashemite

Cited by 27 publications

References 50 publications

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

Crystalline-Size Dependence of Dual Emission Peak on Hybrid Organic Lead-Iodide Perovskite Films at Low Temperatures

Pressure and Temperature Study on the Structural Stability of GdNbO4:Eu3+

High-Pressure Single-Crystal X-ray Diffraction of Lead Chromate: Structural Determination and Reinterpretation of Electronic and Vibrational Properties

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Pressure and Temperature Study on the Structural Stability of GdNbO₄:Eu³⁺