Effect of Nb and Fe co-doping on microstructure, dielectric response, ferroelectricity and energy storage density of PLZT

Abstract

The studies on the effect of simultaneous doping of donor (Nb) and acceptor (Fe) (0–8 at.% of each dopant) in PLZT (Pb0.97La0.02Zr0.52Ti0.48O3), on the dielectric response, ac conductivity and ferroelectricity are reported in this article. It is observed that the value of dielectric constant decreases, dielectric loss increases (moderately) and coercive field increases upon doping of Nb and Fe together. These indicate a hardening like effect as a result of the donor–acceptor co-doping. The ferroelectric to paraelectric phase transition occurs at lower temperatures for higher doping concentrations. For undoped PLZT the Curie temperature is around 353 °C which shifts to 305 °C for 8% Nb–Fe co-doped PLZT. Microstructure studies on the surface, as well as the interior of the samples are carried out which reveal a clear difference. The grain size is observed to decrease with doping concentration. The “true switchable polarization” is deduced by positive up negative down (PUND) tests and found to decrease with doping. Fatigue behavior is found to be positively enhanced upon co-doping of 2% Nb and Fe. Leakage current tests are carried out and it is found that the samples become more ‘leaky’ upon co-doping of Nb and Fe. The energy storage density is also investigated for these Nb–Fe co-doped PLZT ceramics. The highest recoverable energy storage density is observed for 2% Nb–Fe co-doped PLZT sample and it is around 134 mJ/cm3 with an efficiency of 0.28.