High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO<sub>4</sub>

Errandonea, Daniel; Múñoz, A.; Rodríguez‐Hernández, P.; Gomis, O.; Achary, S.N.; Popescu, Cătălin; Patwe, S. J.; Tyagi, A. K.

doi:10.1021/acs.inorgchem.6b00503

Cited by 65 publications

(69 citation statements)

References 62 publications

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“…In the table we have included a column to show the relative difference between experimental and theoretical frequencies, R ω , as defined in Ref. 52. For most modes R ω is smaller than 5% and in many modes even smaller than 1%, which illustrates the excellent agreement between calculations and experiments.…”

Section: Gpa During Compressionmentioning

confidence: 90%

Monazite-type SrCrO4 under compression

et al. 2016

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We report a high-pressure study of monoclinic monazite-type SrCrO 4 up to 26 GPa. Therein we combined x-ray diffraction, Raman and optical-absorption measurements with ab initio calculations, to find a pressure-induced structural phase transition of SrCrO 4 near 8-9 GPa. Evidence of a second phase transition was observed at 10-13 GPa. The crystal structures of the high-pressure phases were assigned to the tetragonal scheelite-type and monoclinic AgMnO 4 -type structures. Both transitions produce drastic changes in the electronic band gap and phonon spectrum of SrCrO 4 . We determined the pressure evolution of the band gap for the low-and high-pressure phases as well as the frequencies and pressure dependences of the Raman-active modes. In all three phases most Raman modes harden under compression; however the presence of low-frequency modes which gradually soften is also detected. In monazite-type SrCrO 4 , the band gap blue-shifts under compression, but the transition to the scheelite phase causes an abrupt decrease of the band gap in SrCrO 4 . Calculations showed good agreement with experiments and were used to better understand the experimental results. From x-ray diffraction studies and calculations we determined the pressure dependence of the unit-cell parameters of the different phases and their ambient-temperature equations of state. The results are compared with the high-pressure behavior of other monazites, in particular PbCrO 4 . A comparison of the high-pressure behavior of the electronic properties of SrCrO 4 (SrWO 4 ) andPbCrO 4 (PbWO 4 ) will also be made. Finally, the possible occurrence of a third structural phase transition is discussed. † ERASMUS student from Imperial College London, London SW7 2AZ, United Kingdom * Corresponding author, email: daniel.errandonea@uv.es 2 I. IntroductionPhotocatalytic materials which respond to ultra-violet (UV) and visible (VIS) light can be used in a wide variety of environmental applications [1]. As a consequence, they have received much attention in recent years. In particular, progress has been made thanks to the development of chromium-based compounds [1]. Among them, lead chromate (PbCrO 4 ) and strontium chromate (SrCrO 4 ) are the most studied materials due to their unique properties [2 -5]. The crystal structures of these ternary oxides have been determined accurately [6], both being assigned to a monazite-type structure (space group P2 1 /n, Z = 4). A schematic view of the monazite structure is given in Fig. 1.The structural arrangement is based on the nine-fold coordination of the Pb (Sr) cation and the fourfold coordination of the Cr cation. The ambient-pressure lattice vibrations and electronic band structures of PbCrO 4 and SrCrO 4 have already been studied too [7]. During the last decade, high pressure (HP) has been shown to be an efficient tool for improving the understanding of the physical properties of ternary oxides [8 -15]. In particular, numerous monazite-type oxides have already been the subject of HP studies [16 -19], which have concentrat...

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Section: Gpa During Compressionmentioning

confidence: 90%

Monazite-type SrCrO4 under compression

et al. 2016

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“…Depending on the compound, the average A-O distance ranges from 2.2 to 2.5 Å. The typical distortion index of the bond length is 0.06 [67]. Because of the structural characteristics described above, the principal structural unit in zircon can be described as a succession of alternating VO4 and AO8 polyhedral units running parallel to the crystallographic c-axis.…”

Section: Crystal Structurementioning

confidence: 99%

“…The examples of this does not limit to the compounds discussed here but also include other oxides like AgClO4 [224] and BaSO4 [225]. On top of that, crystal-chemistry hypotheses have been used to explain the fact that the crystal structure of BiSbO4 remains stable up to at least 70 GPa [67]. Consequently, the arguments presented in this section can be used as tool to make back-of-the-envelope predictions of HP phases in…”

Section: Common Trends Of Pressure-induced Phase Transitionsmentioning

confidence: 99%

“…The understanding of the pressure stability limits of monazite and zircon structures is also for the use of vanadates and chromates as catalysts [259,260] as well as of several oxides as ionic conductors [261] and oxidation-resistant ceramic toughening components [262]. A less obvious application on the knowledge gained from the HP study of monazites, in particular of the optical properties of chromates [67,263], is the explanation of instabilities in paintings [264]. In particular, in those known as chrome yellow, a group of synthetic inorganic pigments that were broadly used as an artistic painting from the 19 th century.…”

Section: Technological and Geophysical Implicationsmentioning

confidence: 99%

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Recent progress on the characterization of the high-pressure behaviour of AVO4 orthovanadates

Errandonea

Garg

2018

Progress in Materials Science

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116

143

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AVO4 orthovanadates are materials of fundamental and technological importance due to the large variety of functional properties exhibited by them. These materials have potential applications such as scintillators, thermophosphors, photocatalysts, and cathodoluminescence materials among others. They are also used as laser-host crystals.Studies at high pressures and temperatures are helpful for understanding the physical properties of the solid state, in particular, the phase behaviour of AVO4 materials. For instance, they have contributed to the understanding of the macroscopic properties of orthovanadates in terms of microscopic mechanisms. A great progress has been made in the last decade towards the study of the pressure-effects on the structural, vibrational, and electronic properties of AVO4 compounds. Thanks to the combination of experimental and theoretical studies, novel metastable structures with interesting * Corresponding author, Email: daniel.errandonea@uv.es, Fax: (34) 96 3543146, Tel.: (34) 96 354 4475 physical properties have been discovered and the high-pressure structural sequence followed by AVO4 oxides has been understood. In this article, we will review highpressure studies carried out on the phase behaviour of different AVO4 compounds. The studied materials include rare-earth orthovanadates and other compounds; for example, BiVO4, FeVO4, CrVO4, and InVO4. In particular, we will focus on discussing the results obtained by different research groups, who have extensively studied orthovanadates up to pressures exceeding 50 GPa. We will make a systematic presentation and discussion of the different results reported in the literature. In addition, with the aim of contributing to the improvement of the actual understanding of the high-pressure properties of ternary oxides, the high-pressure behaviour of orhovanadates will be compared with related compounds; including phosphates, chromates, and arsenates. The behaviour of nanomaterials under compression will also be briefly described and compared with their bulk counterpart. Finally, the implications of the reported studies on technological developments and geophysics will be commented and possible directions for the future studies will be proposed.

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“…54 In this section we will analyze the pressure dependence of the different bond distances of the four polyhedral of MgSO 4 and relate it with their compressibility. Table 7 shows the calculated bond distances at selected pressure for each polymorph.…”

Section: Bond Compressibilitymentioning

confidence: 99%

New pressure-induced polymorphic transitions of anhydrous magnesium sulfate

et al. 2017

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Abstract:The effects of pressure on the crystal structure of the three known polymorphs of magnesium sulfate (α-MgSO 4 , β-MgSO 4 , and γ-MgSO 4 ) have been theoretically study by means of density-functional theory calculations up to 45 GPa. We determined that at ambient conditions γ-MgSO 4 is an unstable polymorph, which decompose into MgO + SO 3 , and that the response of the other two polymorphs to hydrostatic pressure is non-isotropic.Additionally we found that at all pressures β-MgSO 4 has a largest enthalpy than α-MgSO 4 .This indicates that β-MgSO 4 is thermodynamically unstable versus α-MgSO 4 and predicts the occurrence of a β−α phase transition under moderate compression. Our calculations also predict the existence under pressure of additional phase transitions to two new polymorphs of MgSO 4 , which we named as δ-MgSO 4 and ε-MgSO 4 . The α−δ transition is predicted to occur at 17.5 GPa, and the δ−ε transition at 35 GPa, pressures that nowadays can be 2 experimentally easily achieved. All the predicted structural transformations are characterized as first-order transitions. This suggests that they can be non-reversible, and therefore the new polymorphs could be recovered as metastable polymorphs at ambient conditions. The crystal structure of the two new polymorphs is reported. In them, the coordination number of sulfur is four as in the previously known polymorphs, but the coordination number of magnesium is eight instead of six. In the article we will report the axial and bond compressibility for the four polymorphs of MgSO 4 . The pressure-volume equation of state of each phase is also given, which is described by a third-order Birch-Murnaghan equation. The values obtained for the bulk modulus are 62 GPa, 57 GPa, 102 GPa, and 119 GPa for α-MgSO 4 , β-MgSO 4 , δ-MgSO 4 , and ε-MgSO 4 , respectively. Finally, the electronic band structure of these four polymorphs of MgSO 4 has been calculated by the first time. The obtained results will be presented and discussed.

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High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO₄

Cited by 65 publications

References 62 publications

Monazite-type SrCrO4 under compression

Monazite-type SrCrO4 under compression

Recent progress on the characterization of the high-pressure behaviour of AVO4 orthovanadates

New pressure-induced polymorphic transitions of anhydrous magnesium sulfate

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High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4

Cited by 65 publications

References 62 publications

Monazite-type SrCrO4 under compression

Monazite-type SrCrO4 under compression

Recent progress on the characterization of the high-pressure behaviour of AVO4 orthovanadates

New pressure-induced polymorphic transitions of anhydrous magnesium sulfate

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High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO₄