Development of ferroelectric ceramics with high dielectric constant and low dissipation factor for high-voltage capacitors

Both ferroelectric BaTiO3-based and SrTiO3-based dielectric ceramics with high dielectric constant and low dissipation factor have been successfully developed, and applied into mass production for high-voltage ceramic capacitors. Crystalline phases of the ceramics were identified by XRD. STEM study of the ceramics was also conducted. Based on the computer simulation of a shell-core and two-phase mixed structural model proposed, a novel processing method was employed to produce SrTiO3-based ceramics with the following satisfactory dielectric properties: dielectric constant at room temperature epsilon(20'C) = 2000, dissipation factor at room temperature D-20'C = 0.003, temperature coefficient of dielectric constant alpha(epsilon) = - 8% (-25 degrees C to 85 degrees C), and, breakdown electric field E-b = 10kV/mm (dc). Optional composition of BaTiO3-based ceramics has been obtained through the orthogonal design experimentation: BaTiO3-xBaZrO(3)-yBaSnO(3), where x = 8 wt% and y = 6 wt%, with minor additions of MnSiO3, WO3, CeO2, Bi-2(SnO3)(3) and ZnO. Its major properties are as follows: Curie temperature T-c = 21 degrees C, epsilon(20'C) = 18,000, D-20'C = 0.008, alpha(epsilon) = -80% (-25 degrees C similar to +85 degrees C) and E-b = 8kV/mm (dc).