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)O3 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.