Tetrahedrally valanced

The average valance of the Ti component can be pushed toward 4.0 by valence induction, simply by increasing the amount of Li present relative to that of titanium, to give a formula Li1+xTi2 x04. This is equivalent to acceptor doping of the phase. The additional Li+ ions enter the octahedral sites, as the tetrahedral sites are already occupied, to a maximum of Li [Li (nTi nJCL and the acceptor doping is balanced by holes. In order to write formal defect equations for this situation, it is convenient... 

As shown schematically in Figure 2 the stereochemistry at the metal-ligand site may be planar (lb), tetrahedral (Ic), or octahedral (Hb), depending on the valance state of the metal ion and the distribution of electrons in the orbitals of the metal ions. 

Fig. 3(A) shows the UV-Vis spectra of 0.1SnO2-MSM samples before and after calcination synthesized with varied periods of HT in comparison to that of commercial SnOa. Two absorption bands with maximum intensities at 220 and 270 nm were observed for the commercial SnOa. The former was assigned to the ligand to metal charge transfer (LMCT) transition from O to Sn, which was at octahedral (Oh) site. The latter band was the electron transition from the valance to conduction bands (band gap ca. 3.76 eV for bulk SnOa) [1]. Only one broad band of very weak intensity was observed in the spectra of the O.lSnOa-MSM samples before calcination, while two bands at 215 and 253 nm were seen for the samples after calcination. The broad band at ca. 205 210 nm for the uncalcined samples was assigned to the LMCT band of 0 to tetrahedral (Td) Sn ions in the silica lattice [17]. When the HT period was prolonged to 24 h, a shoulder appeared ca. 250 nm. These results imply that the Sn02 nanoparticles were probably formed after the HT treatment for 24 h.

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