Electrical properties of (Cs1−xAx)Al0.33Te1.67O6 (A = K and Rb) mixed valence pyrochlores

Waehayee, Anurak; Eknapakul, Tanachat; Chanlek, Narong; Kongnok, Thanundon; Rattanasuporn, Surachet; Nakajima, Hideki; Meevasana, W.; Siritanon, Theeranun

doi:10.1016/j.jallcom.2017.05.025

Cited by 16 publications

(6 citation statements)

References 34 publications

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“…However, the CsV 0.75 Te 1.25 O 6 compound possesses noticeably low E a value than E g , which could be related to complex band gap structure. The same behavior has been observed previously for β‐pyrochlores with composition of AAl 0.33 Te 1.67 O 6 (A=K, Rb, Cs), [11b,16a] where the activation energy of conduction also increases in the row Cs→Rb→K. The changes between optical band gap and activation energy could be explained by defect crystal structure as well as small amount of V 3+ , which produces mixed valence compounds.…”

Section: Resultssupporting

confidence: 83%

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Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

et al. 2023

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Two new isostructural compounds with composition of Rb + V 3 + 0.125 V 5 + 0.625 Te 6 + 1.25 O 6 and Cs + V 3 + 0.125 V 5 + 0.625 Te 6 + 1.25 O 6 have been synthesized by solid-state reaction. The crystal structure has been determined by X-ray diffraction analysis using Rietveld refinement. Both compounds possess β-pyrochlore structuretype with cubic space group Fd-3 m (Z = 8); the unit cell parameters: a = 10.04120(27) Å for RbV 0.75 Te 1.25 O 6 Å and a = 10.09119(23) Å for CsV 0.75 Te 1.25 O 6 . The oxidation states of vanadium and tellurium have been confirmed by X-ray photoelectron spectroscopy. The compounds contain vanadium in mixed valence state (3 + and 5 +). The compounds possess the unusual narrow band gap for oxide compounds -in the infrared (IR) range (~0.6 eV). The schematic electronic structure of the compounds has been estimated using XPS, UPS and electronic conductivity data; however, the shifts of the top of the valence edge and the bottom of the conduction band in the water conditions have been calculated using theoretical approximation. The thermal behavior of obtained compounds has been studied by differential thermal analysis. RbV 0.75 Te 1.25 O 6 and CsV 0.75 Te 1.25 O 6 melts at low temperatures (~500 °C) with decomposition and weight loss. The RbV 0.75 Te 1.25 O 6 powder decomposes to amorphous phase, whereas CsV 0.75 Te 1.25 O 6 transform into new β-pyrochlore compound with another composition.

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Section: Resultssupporting

confidence: 83%

“…The single component of Te 3d peak was found at binding energy 576.4 � 0.2 eV for Te 6 + , which are in agreement with data for similar compounds. [7,16] No impurities of Te 4 + at 575.7 � 0.2 eV have been detected. [17] Figure 3 c, d shows the V 2p region for RbV 0.75 Te 1.25 O 6 and CsV 0.75 Te 1.25 O 6 .…”

Section: Resultsmentioning

confidence: 94%

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

et al. 2023

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“…Increasing the polarizing ability of A decreases the possibility of β-pyrochlore phase formation by the solid-state method. For example, K-containing phases of A I M V MoO 6 compounds (A I = Rb, Cs; M V = Nb, Ta) were not obtained, and Li- and Na-containing A I M V WO compounds (A I = K, Rb, Cs; M V = Nb, Sb, Ta) were obtained using only the ion exchange reaction…”

Section: Resultsmentioning

confidence: 92%

“…Thus, via simultaneously changing the elemental composition and retaining the crystal structure type, various useful properties can be controlled. For example, the conductivity, band gap, and band edge position of β-pyrochlores AAl 0.33 Te 1.67 O 6 (A = Cs, Rb, and K) strongly depend on the atom in the A site . Also, the influence of atoms in the B site is significant, which appears in the increasing resistivity of CsAl x Te 2– x O 6 solid solutions with rising of Al content .…”

Section: Introductionmentioning

confidence: 99%

“…For example, the conductivity, band gap, and band edge position of βpyrochlores AAl 0.33 Te 1.67 O 6 (A = Cs, Rb, and K) strongly depend on the atom in the A site. 6 Also, the influence of atoms in the B site is significant, which appears in the increasing resistivity of CsAl x Te 2−x O 6 solid solutions with rising of Al content. 7 Even low concentration substitution can lead to strong changes; for example, the average grain size of Li 1−x Na x NbO 3 (to 3 mol %) solid solutions crucially decreases with an increase of sodium content.…”

Section: ■ Introductionmentioning

confidence: 99%

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Solid Solutions Rb_0.95Nb_xMo_2–xO_6.475–0.5x (x = 1.31–1.625) with Orthorhombic β-Pyrochlore Structure: Thermal Behavior and Electronic Structure of β-Pyrochlores Compounds Based on [Nb(Ta)/Mo] Octahedral Framework

et al. 2020

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Solid solutions Rb 0.95 Nb x Mo 2−x O 6.475−0.5x (x = 1.31−1.625) having a β-pyrochlore structure with an orthorhombic system were synthesized by solid-state reaction. The elemental composition was confirmed by X-ray microanalysis. The Rb 0.95 Nb 1.375 Mo 0.625 O 5.79 structure refinement was performed using the Rietveld method. The crystal structure consists of ordered O−Mo−O chains partly occupied by Nb atoms. The oxygen vacancies are necessary to save the electroneutrality of the unit cell. It predominantly appears between Mo atoms that lead to form two disconnected defect octahedra [MoO 5 □•••MoO 5 □].The structural defects cause the low thermal stability; the compounds obtained decompose in the 748−758 °C temperature range. The high-temperature phase transition of the CsNbMoO 6 and CsTaMoO 6 nonlinear optical β-pyrochlores has been studied by differential thermal analysis, differential scanning calorimetric analysis, high-temperature X-ray diffraction analysis, and second harmonic generation analysis. At room temperature the compounds possess the cubic noncentrosymmetric F4̅ 3m cell. Under heating to 437 °C and 401 °C for CsNbMoO 6 and CsTaMoO 6 , respectively, they undergo transition into centrosymmetric Fd3̅ m modification. This is accompanied by the SHG signal disappearing, as well as the 402 reflection, which is characteristic of the F4̅ 3m space group. The positions of the valence and conduction bands were determined by reflectance spectra and XPS analysis for structure-related β-pyrochlores CsNbMoO 6 , CsTaMoO 6 , and Rb 0.95 Nb 1.375 Mo 0.625 O 5.79 .

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Crystal Structure and Photocatalytic Properties of the CsV_0.625Te_1.375O₆ Mixed‐Valence β‐Pyrochlore Compound

et al. 2023

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A new β‐pyrochlore compound with complex composition of Cs(V3+0.0625V5+0.5625Te4+0.34375Te6+1.03125)O6 has been synthesized by a solid‐state reaction and characterized by single‐crystal X‐ray diffraction and thermal analysis. The compound possesses the typical cubic symmetry with space group , however some of the oxygen atoms shift from the special position 48 f to the general crystallographic positions 32e, 96 g and 96 h. This shift is caused by complex B‐site composition with mixed‐valence vanadium and tellurium atoms, especially the presence of the large Te4+ ion. The locations of the valence band and conduction band edges were determined experimentally under vacuum conditions by X‐ray photoelectron spectroscopy, UV‐visible and impedance spectroscopy and evaluated theoretically for water solutions. The photocatalytic ability of the compound under visible light irradiation was determined using the methylene blue decomposition process as an example. The nature of the active radical species and possible dye degradation pathway were suggested according to experimental data.

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Electrical properties of (Cs1−xAx)Al0.33Te1.67O6 (A = K and Rb) mixed valence pyrochlores

Cited by 16 publications

References 34 publications

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

Solid Solutions Rb_0.95Nb_xMo_2–xO_6.475–0.5x (x = 1.31–1.625) with Orthorhombic β-Pyrochlore Structure: Thermal Behavior and Electronic Structure of β-Pyrochlores Compounds Based on [Nb(Ta)/Mo] Octahedral Framework

Crystal Structure and Photocatalytic Properties of the CsV_0.625Te_1.375O₆ Mixed‐Valence β‐Pyrochlore Compound

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Electrical properties of (Cs1−xAx)Al0.33Te1.67O6 (A = K and Rb) mixed valence pyrochlores

Cited by 16 publications

References 34 publications

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A2O‐V2O5‐2TeO3 (A=Rb, Cs) System

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A2O‐V2O5‐2TeO3 (A=Rb, Cs) System

Solid Solutions Rb0.95NbxMo2–xO6.475–0.5x (x = 1.31–1.625) with Orthorhombic β-Pyrochlore Structure: Thermal Behavior and Electronic Structure of β-Pyrochlores Compounds Based on [Nb(Ta)/Mo] Octahedral Framework

Crystal Structure and Photocatalytic Properties of the CsV0.625Te1.375O6 Mixed‐Valence β‐Pyrochlore Compound

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Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

Narrow Band Gap Compounds with β‐Pyrochlore Structure in the A₂O‐V₂O₅‐2TeO₃ (A=Rb, Cs) System

Solid Solutions Rb_0.95Nb_xMo_2–xO_6.475–0.5x (x = 1.31–1.625) with Orthorhombic β-Pyrochlore Structure: Thermal Behavior and Electronic Structure of β-Pyrochlores Compounds Based on [Nb(Ta)/Mo] Octahedral Framework

Crystal Structure and Photocatalytic Properties of the CsV_0.625Te_1.375O₆ Mixed‐Valence β‐Pyrochlore Compound