Dielectric ceramic and dielectric device

Abstract

A dielectric ceramic is made of a sintered body of a complex oxide including at least one element selected from the group consisting of Zr, Ti and Mn, at least one element selected from the group consisting of Mg, Zn and Co, and at least one element selected from the group consisting of Nb and Ta, wherein, the complex oxide is represented by a formula xZrO -yTiO -zA B O where 'A' in the formula denotes at least one element selected from the group (A) consisting of Mg, Zn and Co, 'B' denotes at one element selected from the group (B) consisting of Nb and Ta; x, y, z and w denote values in the respective ranges of 0.20≦x≦0.55, 0.40≦y≦0.55, 0.05≦z≦0.25, and 0≦w≦0.30, and x, y and z have a relationship represented as x+y+z=1; MnO is present in a range of 0.1 mol % to 1.0 mol % to the complex oxide; and an average grain size of the dielectric ceramic is from 10 &mgr;m to 70 &mgr;m, thereby providing a dielectric ceramic that has a high dielectric constant (&egr;r) and an unloaded (Qu) value even in a comparatively low frequency region as a microwave region i.e., in a range of 0.4 GHz to 2.4 GHz and that realizes a desired temperature coefficient (&tgr;f) of a resonant frequency with a high mechanical strength, and thus a dielectric device using the dielectric ceramic is provided.