Abstract Doped nano-ceria particulates ((Ce 0.9 Gd 0.1 )O 2 , GDC) were synthesized by hydrothermal processes and dispersed within a matrix of copper-doped bismuth vanadate (Bi 2 V 0.9 Cu 0.1 O 5.35, BICUVOX) powder at levels ranging from 0.2 to 4.0 wt.%. The BICUVOX powder was synthesized by a co-precipitation process which resulted in a homogenous, fine-grained powder with an average particle size of ~ 0.6 μm. The BICUVOX/GDC composite was sintered at temperatures between 675 and 800 °C for 4 h. The incorporation of the nano-GDC into the BICUVOX ceramic was shown to pin grain boundary mobility, which permitted sintering to high densities while retaining finer grain sizes (1–4 μm in average size). The low levels of nano-GDC additions were shown to decrease the total conductivity of the BICUVOX electrolytes. Four-point conductivity testing of the BICUVOX/GDC (0.6 wt.%) composite in air showed values of ~ 0.008 S/cm and ~ 0.06 S/m at 300 °C and 500 °C, respectively. The average flexure strength of the same composite membrane was measured using a ring-on-ring configuration, and this measurement showed flexural strengths as high as 134.2 MPa. This strength is ~ 60% greater than previously reported values for BICUVOX membranes.