Chromium doped barium titanyl oxalate (BCTO) particles with sandwich-like morphologies were synthesized via a facile chemical co-precipitation method in the presence of acrylamide. The morphologies, structures as well as dielectric and electrorheological (ER) properties of the as-synthesized BCTO particles were studied as functions of the concentration of acrylamide. The results show that with increasing the concentration of acrylamide used in the chemical co-precipitation process, the morphologies of the as synthesized products change from an irregular shape via sandwich-like structure to congeries of blocks, at the same time, the crystallinity and the BET surface area (S-BET) exhibit maximal values. All these phenomena are reasonably explained in terms of the interaction between acrylamide and BCTO. Among the as-synthesized products with various morphologies, the BCTO sandwich-like particles show the strongest interfacial polarization and ER effect, which originate from their peculiar morphology and S-BET. (C) 2010 Elsevier B.V. All rights reserved.