The origin of low bandgap and ferroelectricity of a co-doped BaTiO3 D. Phuyal, S. Mukherjee, S. Das, S. Jana, K. O. Kvashnina, D. D. Sarma, H. Rensmo, S. M. Buortin and O. Karis EPL, 124 2 (2018) 27005 Published online: 19 November 2018 DOI: 10.1209/0295-5075/124/27005