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

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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 ɛ20′C=2000, dissipation factor at room temperature D 20′C=0.003, temperature coefficient of dielectric constant αɛ = −8% (−25°C to 85°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-xBaZrO3-yBaSnO3, where x = 8wt% and y = 6wt%, with minor additions of MnSiO3, WO3, CeO2, Bi2(SnO3)3 and ZnO. Its major properties are as follows: Curie temperature T c = 21°C, ɛ20C=18,000, D 20'C = 0.008, αɛ=−80% (−25°C∼+85°C) and E b = 8kV/mm (dc).