Oxygen vacancy-induced plasmonic and polaronic excitations in rubidium- and potassium-doped hexagonal tungsten bronzes

Absorption peak decomposition of an inhomogeneous nanoparticle ensemble of hexagonal tungsten bronzes using the reduced Mie scattering integration method

“…This indicates that the amount of V O should decrease in the same dopant order because the alkali content was fixed at x = 0.33. Chemical and XRD Rietveld analyses of sintered bulk HTBs yielded the same results of the decreasing V O as Cs → Rb → K 35 .…”

“…All the other compositions were single phased. Further structural details including small unsymmetric strains due to pseudo Jahn–Teller distortion are reported elsewhere 35 .…”

“…See ref. 35 ). If the alkali dopant alone caused the NIR absorption 36 – 38 , such changes are not expected.…”

“…NIR absorption from a single NP of an alkali HTB is contributed by LSPR⊥ and LSPRǁ of free electrons and polaronic transition of trapped electrons 2 , 4 , 35 . The optical behavior of free electrons is described by the Drude oscillator in the free electron model, whereas the interband transitions of trapped electrons is described by the Lorentz oscillator.…”

“…Table 1 also reveals changes in the physical properties of NPs relative to the bulk properties. For instance, Ω p is notably smaller in the NPs than in bulk crystals (bulk data given in 35 ). Figure 7 compares the dielectric functions of a single NP derived from the data in Table 1 with those in bulk crystals.…”