NaCu(Ta1−yNby)4O11 solid solution: A tunable band gap spanning the visible-light wavelengths

Palasyuk, Olena; Maggard, Paul A.

doi:10.1016/j.jssc.2012.03.023

Cited by 17 publications

(27 citation statements)

References 39 publications

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“…In principle on all the three cation positions A1, A2 and A3 a cation exchange can be done, but since recent studies in niobate/tantalate systems have shown that the substitution of the Nb site with tantalum (Ta) could considerably improve the photocatalytic activity, [16][17][18] we concentrated on this substitution. However, most reports of substitution effects are focused on the photodegradation of organic compounds.…”

Section: Introductionmentioning

confidence: 99%

Tetragonal tungsten bronze-type nanorod photocatalysts with tunnel structures: Ta substitution for Nb and overall water splitting

et al. 2014

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Section: Introductionmentioning

confidence: 99%

Tetragonal tungsten bronze-type nanorod photocatalysts with tunnel structures: Ta substitution for Nb and overall water splitting

et al. 2014

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“…This strategy is based on requiring the cations to diffuse over longer distances to phase segregate into the simpler oxides, such as Nb 2 O 5 and Ta 2 O 5 . Many recent examples from my group have illustrated this concept, including the single metal-site (M) solid solutions of CuNb 1– x Ta x O 3 , Cu 5 Ta 11– x Nb x O 30 , and NaCu(Ta 1– x Nb x ) 4 O 11 . ,, These compounds show that Nb(V) and Ta(V) will statistically disorder over the same crystallographic sites owing to their nearly identical Shannon radii. More complex examples are the double metal-site (both M and M′) solid solutions, including (Ba 1– x Sn x )(Zr 1– y Ti y )O 3 and (Na 2– x Sn x /2 )(Ta 4– y Nb y )O 11 , , with the cations separated by parentheses in the chemical formula.…”

Section: Mixed-metal Oxide (M′mo X ) Semiconductorsmentioning

confidence: 99%

Capturing Metastable Oxide Semiconductors for Applications in Solar Energy Conversion

Maggard

2021

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Many small bandgap semiconductors have been discovered or predicted to exist beyond the edges of stability, that is, accessible only as metastable solids that are thermodynamically unstable. In many cases, these metastable semiconductors have been revealed to have technologically promising properties for solar energy conversion, such as in photocatalysis or in photovoltaics. This Account presents a review of research results selected from my group and others in recent years on these semiconductors. Notably, these include the chemical systems of mixed-metal oxides (i.e., M′MO x ; M = Ti(IV), Nb(V), or Ta(V) cation; M′ = Ag(I), Cu(I), Sn(II), Pb(II), or Bi(III) cation), which have diverse structure types and compositions. High photocatalytic activities have been found for the light-driven reduction or oxidation of water as p-or n-type photoelectrodes, respectively, or as suspended powders in aqueous solutions. These have exhibited new combinations of favorable semiconductor properties, such as deep visible-light absorption, near-optimal band edge energies, defect tolerance, and functional carrier mobilities and charge separation. As described herein, this set of properties is inextricably linked to their metastable nature, that is, the crystalline structures and compositions needed for these characteristics lead naturally to thermodynamic instabilities. This Account focuses on current research efforts that have begun unlocking the potential of these semiconductors via new recent advances in (1) synthetic approaches that enable their preparation and (2) the understanding of structure−property relationships discovered at the precipices of stability that lead to the improved semiconductor properties. For example, low-temperature reactions have been developed to facilitate greater kinetic control, such as with the use of molten salts, and have been a key factor in preparing many of these semiconductors. As a result, a plethora of promising new mixed-metal oxide systems have been uncovered that exhibit band gaps spanning the range of photon energies from ∼1.3 to >3.0 eV. Especially relevant for visible-light applications are the Cu(I)-and Sn(II)-containing semiconductors. For example, n-type Sn(II)-titanates and p-type Cu(I)-niobates can be synthesized by flux methods and exhibit some of the smallest known visible-light band gaps that also maintain suitable conduction and valence band edges for driving the water-splitting half reactions. Kinetic stabilization of these metastable semiconductors against thermally driven phase segregation is increased with the formation of solid solutions for both the M and M′ cation sites, leading to effective strategies to more finely tune their band gaps, band edge energies, and photoelectrochemical properties. Many unique and useful relationships are emerging between the synthesis and structures of metastable semiconductors and their physical properties, leading to more efficient solar energy conversion.

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“…Such a trigonal phase, whose atomic structure is similar to that of the natural natrotantite mineral Na 2 Ta 4 O 11 [27,28], has been found to exhibit interesting properties of piezoelectricity [16,29]. Through different atomic substitutions (e.g., Ta 5+ by Nb 5+ , Na + by Cu + or Ag + ) it exhibits also photo-catalytic [30,31] ferroelectric and non-linear optical properties [32][33][34]. Table 1) Table 1 (Integrated peak intensities are normalised to a same value for a comparison between them).…”

Section: Crystallisation Under Pure Oxygenmentioning

confidence: 99%

Particular structural defects in Ta2O5 from crystallisation of amorphous thin films in O2–H2O atmosphere

et al. 2015

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NaCu(Ta1−yNby)4O11 solid solution: A tunable band gap spanning the visible-light wavelengths

Cited by 17 publications

References 39 publications

Tetragonal tungsten bronze-type nanorod photocatalysts with tunnel structures: Ta substitution for Nb and overall water splitting

Tetragonal tungsten bronze-type nanorod photocatalysts with tunnel structures: Ta substitution for Nb and overall water splitting

Capturing Metastable Oxide Semiconductors for Applications in Solar Energy Conversion

Particular structural defects in Ta2O5 from crystallisation of amorphous thin films in O2–H2O atmosphere

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