PURPOSE: To decrease the sintering temperature, increase the thermal expansion coefficient and lower the dielectric constant of the subject composition by selecting the composition to fall within a range defined by 6 specific points in a 3-component composition chart composed of Al2O3, MgO and lead borosilicate glass.

CONSTITUTION: The ceramic composition falls on the likes connecting 6 compositional points or within the compositional range enclosed by the 6 points in a 3-component composition chart composed of Al2O3 (X), MgO (Y) and lead borosilicate glass (Z). The 6 points are defined by a (X;0.2, Y;0.28, Z;0.52), b (X;0.2, Y;0.15, Z;0.65). c (X;0.1, Y;0.15, Z;0.75), d (X;0, Y;0.25, Z;0.75), e (X;0, Y;0.4, Z;0.6) and f (X;0.08, Y;0.4, Z;0.52).