The effect of excess titanium and crystal symmetry on electronic properties of Pb(Zr1-xTix)O3 compounds

In this paper the structural and electronic properties including band structure, energy gap and density of states have been studied for different phases of Pb(Zr1-xTix)O-3 compounds with a wide range of Ti/Zr ratio (i.e. from x = 0 to x = 1). The calculations were performed in the framework of density functional theory (DFT), using the full potential-linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). In general, our results show that for all cases (x = 0, 0.33, 0.5, 0.66 and 1) by increasing the amount of Ti atoms the band gap decreases, because of the strong hybridization between Ti-3d and O-2p orbital. But, in other hand, decreasing the crystal symmetry results in widening the band gap. For the monoclinic phase (x = 0.5) the effect of excess Ti on the band gap is less than the effect of crystal symmetry, so there is an increase in the band gap. (c) 2008 Elsevier B.V. All rights reserved.