Switching current in Pb(Zn1/3Nb2/3)03-PbTiO3 single crystals

Switching current measurements have been carried out on relaxor ferroelectric single crystal - pure PZN, and the solid solution (1-x) Pb(Zn_1/3Nb_2/3)0₃ - x PbTiO₃ with x= 0.04, 0.09, 0.10. Measurements have been done for crystallographic directions [001] and [111] for all these compositions. Switching times versus the applied field showed the following results. Pure PZN along [111] and 0.90PZN - 0.10PT along [001], and [111] showed an exponential dependence. Along [001] the PZN showed a linear fit. For solid solution single crystals-0.96PZN -0.04PT and 0.91PZN - 0.09PT, a linear fit was obtained for the reciprocal switch times versus applied field for both the directions. If we draw a parallel picture with the reported barium titanate data, it appears that the polarization reversal is controlled by nucleation along [111]- spontaneous direction for PZN and [001], [111] for 0.90PZN - 0.10PT. The mobility of the reversed domains controls the reversal along [001] for PZN and the solid solution single crystals with rhombohedral composition along [001] and [111]. The transient current curves showed two maximum points for crystals with x = 0.04 and 0.09. This is attributed to the co-existence of the two phases in 0.96PZN -0.04PT and 0.91 PZN - 0.09PT crystals.