Patent ID: 7679485

Claim:
A multilayer positive temperature coefficient thermistor comprising: a ceramic body in which semiconductor ceramic layers having a sintered density in the range of 65% to 90% of a theoretical sintered density and internal electrode layers are alternately laminated to each other; diffusion layers between the semiconductor ceramic layers and the internal electrode layers; and external electrodes formed on two end portions of the ceramic body and electrically connected to the internal electrode layers, wherein a BaTiO 3 -based ceramic material is a primary component in the semiconductor ceramic layers, the ratio of the Ba site to the Ti site of the BaTiO 3 -based ceramic material is represented by 0.998≦Ba site/Ti site≦1.006, at least one element selected from the group consisting of Eu, Gd, Tb, Dy, Y, Ho, Er, and Tm is contained in the semiconductor ceramic layers as a semiconductor dopant in the range of 0.1 to 0.5 molar parts with respect to 100 molar parts of Ti, the internal electrode layers include Ni as a primary component, and a ratio of a thickness t of the diffusion layers and a thickness D of the semiconductor ceramic layers is represented by 0.01≦t/D≦0.20.