Synthesis and optical properties of Cr-doped Ba2In2O5 orange-brown oxides

Lei, Honghong; Zhou, Yuncheng; Jiang, Peng; Wang, Wei; Cao, Wenbin; Xue, Yawen

doi:10.1016/j.ceramint.2018.07.230

Cited by 6 publications

(3 citation statements)

References 26 publications

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“…Using the same model to our new data given in Table 2 would confirm a water content of x = 0.74. However, this neglects the higher oxygen content of 5.32(4) determined by PND (Section 3.3.4) being in accordance with the charge neutrality regarding the stated heterovalent substitution of In 3+ by Cr 6+ [15]. Taking into account the higher oxygen content of the chromium substituted sample, a water content of x ≈ 0.5 (Ba 2 In 1.8 Cr 0.2 O 5.32(4) (H 2 O) 0.5 ) would be in agreement with the present TGA and the previous chemical analysis [3] results.…”

Section: Thermal Analysismentioning

confidence: 70%

“…The refined oxygen content of 5.26 (7) at 873 K (E6) and 5.36(4) at 573 K (D20) is unusual for a brownmillerite-type structure. As indium, oxidation state +3, is substituted by chromium, oxidation state +6 [15], the expected oxygen content needs to be higher (5.3) assuming a charge neutral compound. This is in good agreement with the determined oxygen contents.…”

Section: High-temperature Neutron Diffractionmentioning

confidence: 99%

“…The partial replacement of In by Cr forming Ba 2 In 2−x Cr x O 5±δ has shown a massive performance improvement during photocatalytic CO 2 conversion and oxygen transport [2,4]. An important factor responsible for the improvement is that the brownmillerite-type structure favours the oxidation of Cr 3+ to Cr 6+ [15] during preparation in air, hence turning the initially anticipated isovalent doping or substitution into heterovalent doping, causing remarkable structural changes at low and intermediate temperatures [3,4]. For example, thermogravimetric analysis (TGA) and chemical analysis show the water content to increase by a factor of five [3,4].…”

Section: Introductionmentioning

confidence: 99%

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Effects of Cr Doping and Water Content on the Crystal Structure Transitions of Ba2In2O5

et al. 2021

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Temperature-dependent crystal structure alterations in the brownmillerite-type material Ba2In2O5 play a fundamental role in its applications: (i) photocatalytic CO2 conversion; (ii) oxygen transport membranes; and (iii) proton conduction. This is connected to a reversible uptake of up an equimolar amount of water. In this study, in situ X-ray and neutron diffraction were combined with Raman spectroscopy and solid-state nuclear magnetic resonance experiments to unravel the effects of Cr doping and water content on the crystal structure transitions of Ba2In2O5(H2O)x over a wide temperature range (10 K ≤ T ≤ 1573 K, x < 1). A mixture of isolated and correlated protons was identified, leading to a highly dynamic situation for the protons. Hence, localisation of the protons by diffraction techniques was not possible. Cr doping led to an overall higher degree of disorder and stabilisation of the tetragonal polymorph, even at 10 K. In contrast, a further disordering at high temperatures, leading to a cubic polymorph, was found at 1123 K. Cr doping in Ba2In2O5 resulted in severe structural changes and provides a powerful way to adjust its physical properties to the respective application.

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Section: Thermal Analysismentioning

confidence: 70%

Section: High-temperature Neutron Diffractionmentioning

confidence: 99%