Brief Review of the Effects of Pressure on Wolframite-Type Oxides

Errandonea, Daniel; Ruiz‐Fuertes, J.

doi:10.20944/preprints201801.0070.v1

Cited by 12 publications

(5 citation statements)

References 45 publications

(89 reference statements)

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“…The band-crossing phenomenon discovered near 6.5 GPa in InNbO 4 has been observed for InTaO 4 at a similar pressure (P ~ 7 GPa) [11] and is typical of wolframitetype compounds [10]. For instance, it has been found in CdWO 4 around 5 GPa [54] and it is a consequence of the non-isotropic compressibility of wolframite and the distortion induced by pressure in the TaO 6 (NbO 6 ) octahedron.…”

Section: High-pressure Behavior Of the Band Gapmentioning

confidence: 59%

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High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4

et al. 2019

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We have studied the electronic properties at ambient pressure and under high pressure of InVO 4 , InNbO 4 , and InTaO 4 powders, three candidate materials for hydrogen production by means of photocatalytic water splitting using solar energy. A combination of optical absorption and resistivity measurements and band structure calculations have allowed us to determine that these materials are wide band-gap semiconductors with a band-gap energy of 3.62(5), 3.63(5), and 3.79(5) eV for InVO 4 , InNbO 4 , and InTaO 4 , respectively. The last two compounds are indirect band-gap materials, and InVO 4 is a direct band-gap material. The pressure dependence of the band-gap energy and the electrical resistivity have been determined too. In the three compounds, the band gap opens under compression until reaching a critical pressure, where a phase transition occurs. The structural transition triggers a band-gap collapse larger than 1.2 eV in the three materials, being the abrupt decrease in the band-gap energy related to an increase in the pentavalent cation coordination number. The phase transitions also cause changes in the electrical resistivity, which can be correlated with changes induced by pressure in the band structure. An explanation to the reported results is provided based upon ab initio calculations. The conclusions attained are of significance for technological applications of the studied oxides.

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Section: High-pressure Behavior Of the Band Gapmentioning

confidence: 59%

“…InNbO 4 and InTaO 4 are isostructural compounds which crystallize in the wolframite structure [10]. They belong to the monoclinic space group P2/c, having two formula units per unit cell (Z = 2).…”

Section: Introductionmentioning

confidence: 99%

High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4

et al. 2019

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“…In the lowpressure phase the band-gap slightly blue shifts (see Figure 5) as a consequence of the increase of the splitting between bonding and antibonding states of the tantalate (niobate) ion. 24,25 On the other hand, the structural changes caused by the phase transition trigger a collapse of the band gap to values close to 2.5 eV. This phenomenon is a consequence of the increase of the orbital hybridization, which is related to the decrease of bond distances and the increase of the coordination number of Ta (Nb) at the phase transition.…”

Section: Invo 4 and Related Compoundsmentioning

confidence: 99%

Exploring the high-pressure behaviour of polymorphs of AMO4 ternary oxides: crystal structure and physical properties

Errandonea

2019

J Chem Sci

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AMO 4 ternary oxides are materials of fundamental and technological importance exhibiting a large variety of functional properties. Members of this family of compounds have multiple potential applications; for instance, as scintillators, thermophosphors, photocatalysts, and cathodoluminescence materials. Studies under high-pressure conditions are valuable for understanding the physical properties and phase behaviour of AMO 4 oxides. In particular, great progress has been achieved in the last decade towards the understanding of the pressure-effects on the structural, vibrational, and electronic properties of AMO 4 materials. Specifically, novel metastable structures with interesting physical properties have been discovered. In this article, a selection of recent results from high-pressure studies on different AMO 4 oxides will be discussed, paying particular attention to orthovanadates. Remarkable phenomena like band-gap and volume collapses as well as phonon softening will be discussed and correlated with structural changes.

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“…Ionic conductivity as well as highly anisotropic compression and thermal expansion are thus expected [45][46][47]. Other properties as the bulk modulus can be estimated from empirical relations, assuming that compression is dominated by the ZnO6 and LiO6 octahedra, from the Zn-O and Li-O bond distances and the formal charge of Zn and Li [48]. The obtained value is 55 GPa.…”

Section: Crystal Structurementioning

confidence: 99%

Synthesis, Characterization, and Crystal Structure Determination of a New Lithium Zinc Iodate Polymorph LiZn(IO<sub>3</sub>)<sub>3</sub>

Hebboul¹,

Galez²,

Benbertal³

et al. 2019

Preprint

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Synthesis and characterization of anhydrous LiZn(IO3)3 powders prepared from an aqueous solution are reported. Morphological and compositional analyses were carried out by scanning electron microscopy and energy dispersive X-ray measurements. The synthesized powders exhibit a needle-like morphology after annealing at 400°C. A crystal structure for the synthesized compound has been proposed from powder X-ray diffraction and density-functional theory calculations. Rietveld refinements led to a monoclinic structure, which can be described with space group P21, number 4, and unit-cell parameters a = 21.874(9) Å, b = 5.171(2) Å, c = 5.433(2) Å, and beta = 120.93(4)º. Density-functional theory calculations supported the same crystal structure. Infrared spectra were also collected and the vibrations associated to the different modes discussed. The non-centrosymmetric space group determined for this new polymorph of LiZn(IO3)3, the characteristics of its infrared absorption spectrum, and the observed second harmonic generation suggest a promising infrared non-linear optical material.

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Brief Review of the Effects of Pressure on Wolframite-Type Oxides

Cited by 12 publications

References 45 publications

High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4

High-pressure characterization of the optical and electronic properties of InVO4, InNbO4, and InTaO4

Exploring the high-pressure behaviour of polymorphs of AMO4 ternary oxides: crystal structure and physical properties

Synthesis, Characterization, and Crystal Structure Determination of a New Lithium Zinc Iodate Polymorph LiZn(IO<sub>3</sub>)<sub>3</sub>

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