Abstract: An insulating ceramic compact is provided which can be obtained by low-temperature firing, has a low relative dielectric constant and superior high frequency characteristics, and can be co-sintered with a material having a high coefficient of thermal expansion. The insulating ceramic compact is a fired mixture of an MgAl2O4-based ceramic and a borosilicate glass, in which an MgAl2O4 crystal phase and at least one of an Mg3B2O6 crystal phase and an Mg2B2O5 crystal phase are precipitated as primary crystal phases.

Abstract: An insulative ceramic compact is composed of a fired mixture of (A) a MgAl2O4, Mg3B2O6 and/or Mg2B205 ceramic powder, and (3) a glass powder including from about 13 to 50% by weight of silicon oxide in terms of SiO2, from 8 to 60% by weight of boron oxide in terms of B2O3, about 20% by weight or less of aluminum oxide in terms of A12O3, and from about 10 to 55% by weight of magnesium oxide in terms of MgO. The insulative ceramic compact can be obtained by firing at low temperatures of about 1000° C. or less, can be obtained by sintering with Ag or Cu, has a low dielectric constant and a high Q value, and is suitable for use in the high-frequency range.

Abstract: An insulator ceramic composition making it possible to obtain a sintered material which can be fired at low temperature of 1000° C., can be co-sintered with Ag and Cu, exhibits superior mechanical strength, exhibits high Q value and is appropriate for using high frequencies, is provided. The insulator ceramic composition is composed of (A) an MgO—MgAl2O4 ceramic powder, and (B) a glass powder containing silicon oxide in a proportion of about 13 to 50 weight % in terms of SiO2, boron oxide in a proportion of about 3 to 60 weight % in terms of B2O3, and aluminum oxide in a proportion of 0 to about 20 weight % in terms of Al2O3.

Abstract: An insulating ceramic includes a fired mixture of a MgO—MgAl2O4 ceramic and a borosilicate glass, in which MgAl2O4 crystal phase and at least one of Mg3B2O6 crystal phase and Mg2B2O5 crystal phase are the major crystal phases. The insulating ceramic can be obtained by firing at low temperatures of 1000° C. or less, can be fired in conjunction with Ag or Cu, has a high Q-value and satisfactory mechanical strength, and is suitable for use at high frequencies.