  Effect of uncompensated Ga-V co-doping on structural phase transition, grain
growth process and optical properties of TiO2 is reported here. Inhibition of
phase transition due to co-doping is confirmed by X-ray diffraction
measurement. Activation energy of phase transition increases from 120KJ/mol
(x=0) to 140 KJ/mol (x=0.046) due to Ga-V co-doping. In anatase phase, lattice
constants increase by the effect of Ga3+ interstitials. This results in
inhibition of phase transition. Anatase phase becomes stable up to ~650 C in
co-doped sample whereas for pure TiO2 phase transition starts in between
450-500 C. In anatase phase, strain increases due to co-doping which reduces
crystallite size. In rutile phase, grain growth process is enhanced due to
co-doping and particles show a rod-like structure with majority 110 facets.
Bandgap decreases in both phases and reduced to a visible light region. BET
analysis shows that surface area increases from 4.55 m2/g (x=0) to 96.53 m2/g
(x=0.046) by Ga-V incorporation which provide a large number of active site for
photocatalytic activity. Hence, co-doped anatase nanoparticle can be used as a
promising candidate for photocatalytic applications using visible light up to a
higher temperature ~650 C.
