Corrigendum to "Improved microstructure and sintering temperature of bismuth nano-doped GDC powders synthesized by direct sol-gel combustion" [Ceram. Int. (2018) 3800–3809]. Issue 8 (1st June 2018) - Accardo, G.; Frattini, D.; Ham, H.C.; Han, J.H.; Yoon, S.P.