“…This finding has triggered a burst of research activities on (A + B) co‐doped TiO 2 ceramics. So far, the dual doping in TiO 2 can be clarified into two types: (i) tri‐ and pentavalent ions co‐doping, such as (In 3+ +Nb 5+ /Ta 5+ ), (Sm 3+ +Ta 5+ ), (V 3+ +Nb 5+ ), (Sc 3+ +Nb 5+ ), (Ga 3+ +Nb 5+ /Ta 5+ /Sb 5+ ), (Yb 3+ +Nb 5+ ), (Bi 3+ +Nb 5+ ), (Dy 3+ +Nb 5+ ), (Al 3+ +Nb 5+ /Ta 5+ /Sb 5+ ), (Er 3+ +Nb 5+ ), (Y 3+ +Nb 5+ ), (Tl 3+ +Nb 5+ ), (Eu 3+ +Nb 5+ ), (Pr 3+ +Nb 5+ ), and (La 3+ +Nb 5+ ), (ii) bi‐ and pentavalent ions co‐doping, such as (Ca 2+ +Nb 5+ ), (Mg 2+ +Nb 5+ /Ta 5+ ), and (Zn 2+ +Nb 5+ ) …”