Semiconductor ceramic, monolithic semiconductor ceramic capacitor, method for manufacturing semiconductor ceramic, and method for manufacturing monolithic semiconductor ceramic capacitor

摘要

In a semiconductor ceramic according to the present invention, a donor element within the range of 0.8 to 2.0 mol relative to 100 mol of Ti element is contained as a solid solution with crystal grains, an acceptor element in an amount less than the amount of the donor element is contained as a solid solution with the crystal grains, an acceptor element within the range of 0.3 to 1.0 mol relative to 100 mol of Ti element is present in crystal grain boundaries, and the average grain size of the crystal grains is 1.0 µm or less. A monolithic semiconductor ceramic capacitor is obtained by using this semiconductor ceramic. At that time, in a first firing treatment to conduct reduction firing, a cooling treatment is conducted while the oxygen partial pressure at the time of starting the cooling is set at 1.0 × 10⁴ times or more the oxygen partial pressure in the firing process. In this manner, a SrTiO₃ based grain boundary insulation type semiconductor ceramic having a large apparent relative dielectric constant εr_APP of 5,000 or more and a large resistivity logp (ρ: Ω·cm) of 10 or more even when crystal grains are made fine to have an average grain size of 1.0 µm or less, a monolithic semiconductor ceramic capacitor including the semiconductor ceramic, and methods for manufacturing them are realized.