Electrorheological behavior of rare earth-doped barium titanate suspensions

Doping Y, La, Ce into barium titanate is found to be able to improve its electrorheological (ER) effect in DC electrical field. The yield stress of a typical doped barium titanate/silicone oil suspension is approximately 3.2 kPa at 3.5 kV/mm, which is 10 times larger than that of pure barium titanate/silicone oil suspensions. The ER effect increases with the decrease of ionic radius of rare earth (RE) dopant when RE concentration remains constant, and the suspensions exhibit a relatively high shear stress when Y, La, Ce mote fractions are 15%, 10%-15%, and 5%, respectively. Dielectric measurements show that the suitable doping with RE element increases dielectric loss of barium titanate and causes very marked dielectric relaxation at low frequency. By measuring X-ray diffraction patterns of doped barium titanate, it is considered that the occurrence of lattice distortion or defects may be responsible for the change of dielectric properties which results in the improvement of ER effect of barium titanate in DC electrical field.