Energy band gap and dispersive optical parameters in Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics

Structural, Optical and Electrical Properties of Bi1.5Zn0.92Nb1.5-6x/5WxO6.92 Pyrochlore Ceramics

“…The 12,16 ) spectra for the substituted W-BZN are shown in Figure 3a. In general, the shape of E α − variations is very similar to that we previously observed for the pure BZN pyrochlore ceramics 6 . Namely, the absorption coefficient sharply decreases with decreasing incident photon energy reaching a minima near 5.0 eV where it then tends to remain constant.…”

“…The lattice parameter (a) for the undoped BZN samples was 10.259 Å. This value is comparable with that reported for BZN in literature 5,6 . The samples substituted with tungsten contents of 0.10, 0.15 and 0.18 displayed lattice parameters values of 10.131, 10.082 and 1.157 Å, respectively.…”

“…Earlier studies on the formation of the Bi 2 WO 6 phases in Bi 2-x La x O 6 17 have shown that this compound is formed as a result of partial substitutions of La atoms in sites of Bi atoms in the Bi 2 WO 6 structure. It is mentioned that in this process, the tungsten atom is octahedrally coordinated to oxygen atoms forming WO 4 -layers.…”

“…On the other hand, following our early published procedure 6,19 , the energy band gap is calculated with the help of Tauc's equation 12,18,19 for indirect forbidden transitions…”

Structures and solid solution mechanisms of pyrochlore phases in the systems Bi2O3–ZnO–(Nb, Ta)2O5

“…However, there is uncertainty in the literature as to its precise crystal symmetry and stoichiometry. It has been described as an orthorhombic phase, but recent studies indicated it has a monoclinic unit cell, space group C2/c with a zirconolite-like crystal structure [14][15]17]. In the Ta system, a pyrochlore phase of ideal P stoichiometry exists, but it is one member of a solid solution area with both variable Bi:Ta ratio and a deficiency of Zn.…”