Effect of Sm and Ni co-doping on optical and electrical properties of lead magnesate niobate titanate ceramics.

The ability to manipulate the bandgap while maintaining strong ferroelectricity in perovskite oxides offers numerous functional advantages, including multimodal energy harvesting/sensing, current modulation, dual-source actuation, electric-free poling, and enhanced bulk photovoltaic effect. However, bandgap engineering of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) - renowned for its outstanding piezoelectric properties - via Ni2+ doping remains unexplored, despite its prior success in alkaline niobates. This study provides a comprehensive characterization of the structure-property relationships in Sm/Ni co-doped PMN-PT ceramics, especially for their optoelectrical properties. The results show that Ni2+ doping behaves differently than in alkaline niobates. Nevertheless, Sm/Ni co-doping effectively tunes the phase transition, photoconductivity, charge carrier trapping, and optical absorption while retaining reasonable piezoelectric energy harvesting performance. Overall, this work offers insights into the role of Ni2+ in the band structure of Sm-PMN-PT perovskite and pyrochlore phases.