The optimization of lattice-free volume and lattice symmetry distortion improves the ionic conductivity of the perovskite materials. Here, we report the correlation between structural and electrical properties of A-site substituted monovalent metal cations (Li+, Na+, K+) with various concentrations (10 %, 20 %, and 30 %) in LaAlO3 solid electrolytes synthesized by the glycine-nitrate combustion method. The formation of hexagonal LaAlO3 was confirmed by X-ray diffraction and the maximum internal lattice expansion was observed with the concentrations of 10 % Li+, 10 % Na+, and 20 % K+- doping in LaAlO3. Among the monovalent cations, 10 % of Na-doped LaAlO3 exhibited the highest conductivity, as the ionic radius of Na+(1.39 Å) is close to La3+ (1.36 Å). This substitution minimally distorts the lattice and thus provides more free volume for migration, which was further confirmed by XPS analysis. The maximum enhancement of conductivity of more than an order of 3 magnitudes was observed for monovalent doped LaAlO3 than the pure sample. Our results highlight the increase in conductivity of monovalent doped LaAlO3 in the order of Na+ > Li+ > K+. The results demonstrated that Na-doped LaAlO3 can be a good electrolyte material for intermediate temperature oxide ion conducting solid oxide fuel cells.