In the present study, morphological and electrical properties of BaZrO₃ were investigated as a function of the ionic radii mismatch between Zr and the different B-site dopants (Al, Sc, In, Lu, Tm, Y, Gd, Sm, Nd, and La) for the same solute concentration and valence. Our study highlights the critical role of the ionic radius of the acceptor dopant on stability, sinterability, and proton conductivity of barium zirconate. From our study, Gd-doped barium zirconate emerges as a novel promising material for proton conductor electrolytes.