Hydrothermal synthesis and dielectric properties of lead nickel niobate ceramics

Lead nickel niobate (Pb(Ni1/3Nb2/3)O-3) has been prepared by a newly developed hydrothermal process. During the hydrothermal reaction at 250 degrees C, a pyrochlore phase is formed. After calcining the 250 degrees C-hydrothermally derived precursors at 750 degrees C, a monophasic Pb(Ni1/3Nb2/3)O-3 compound is successfully produced. Increasing the hydrothermal temperature significantly facilitates the formation of the perovskite phase. In comparison with the solid-stale reaction, the hydrothermal process not only reduces the temperature for synthesizing Pb(Ni1/3Nb2/3)O-3, but also decreases its particle size to the submicron range. The dielectric properties of Pb(Ni1/3Nb2/3)O-3 strongly depend on the electric field frequency. Increasing the field frequency results in an increase in the apparent Curie temperature, which is associated with a decrease in the maximum dielectric permittivity. The critical exponent and diffuseness calculated by a modified permittivity-temperature equation verify the relaxer characteristics of Pb(Ni1/3Nb2/3)O-3.