Relationship between Calcining Reactions of MgNb_2O_6 to the Properties of PMN-Based Electrostrictive Ceramics

The studies of initial calcining reactions of MgNb2O6were carried out at different calcining temperatures. The results show that the amount of free MgO exhibits a decreasing with the increase of MgNb2O6 calcining temperature. PMN based electrostrictive ceramics were prepared according to the process described by Swartz et al, but MgNb2O6 was formed without addition of excess MgO at 1050℃. No pyrochlor phase, within the detection limits of X-ray diffractometer was observed in the PMN based ceramics. At room temperature the longitudinal electrostrictive strain (S11) for the ceramics was found to be 1.05×10-3 with only 6.8% hysteresis applied a quasi-static electric field 1kV/mm operating frequencies of 0.07Hz.The relation between calcining temperature of MgNb2O6 and electrostrictive properties of the PMN based cerarnics was also studied. It was obvious that Curie temperature Tc of the PMN based ceramics increases with the increase of calcining temperature of MgNb2O6 and causes the ceramics having lower dielectric constant and larger electric machanical hysteresis.