Barium carbonate crystals with higher-order superstructures have been successfully synthesized in a simple aqueous system containing a general polymer, polyacrylamide (PAM) at room temperature. BaCl2, NaHCO3 and NH3 center dot H2O were used as the starting reagents. The X-ray powder diffraction (XRD) analysis showed the product was the orthorhombic BaCO3. Scanning electron microscopy (SEM) observations showed that higher-order superstructures were formed by the self-assembly of BaCO3 nanorods. Research showed that the morphology of the as-synthesized BaCO3 crystals could gradually evolve with the reaction time. Also, the morphology of BaCO3 crystals was affected by the initial concentrations of reactants: lower concentrations were used for the formation of dumbbell-shaped BaCO3 crystals. Based on the experimental results, a possible formation mechanism of BaCO3 superstructures was discussed. (C) 2008 Elsevier B.V. All rights reserved.