Abstract: Dielectric ceramics comprising a diopside oxide crystal phase, at least one kind of crystal phase selected from the group consisting of a quartz crystal phase and a composite oxide crystal phase containing Ti and Mg or Zn, and a glass phase of an amount of not larger than 30% by weight, said dielectric ceramics having a coefficient of thermal expansion of not smaller than 5.5 ppm/° C. at room temperature to 400° C. and a dielectric loss of not larger than 30×10−4 at 60 to 77 GHz. The ceramics can be obtained by the co-firing with a low-resistance metal such as copper or silver, and can be advantageously used for the production of wiring boards to which the signals of particularly high frequencies are applied. The ceramics has a large coefficient of thermal expansion which can be brought close to the coefficient of thermal expansion of the semiconductor element such as of GaAs or of the printed board.

Abstract: Ceramics for wiring boards having an SiO2 crystal phase, a spinel type oxide crystal phase containing Mg or Zn and Al and a composite oxide type crystal phase containing at least Sr, Al and Si, and having a coefficient of thermal expansion of not smaller than 5.5 ppm/° C. at room temperature through up to 400° C., a dielectric constant of not larger than 7, and a dielectric loss of not larger than 50×10−4 at 20 to 30 GHz. The ceramics can be obtained by the co-firing with a low-resistance metal such as copper or silver, and can be advantageously applied for the production of a wiring board for treating, particularly, signals of high frequencies. Furthermore, the ceramics has a coefficient of thermal expansion which is so large as can be brought close to the coefficient of thermal expansion of the semiconductor element such as GaAs or of the printed board.