The trend to fabricate mulitlayer structures of microwave dielectric ceramics cofired with low melting conductors results in the demand of additives for low temperature sintering. Low-melting glasses are good candidates for low temperature sintering aids. When the concentration of the added low-melting glasses reaches a high content of about 10-20 mol%, their microwave properties will certainly affect the performance of the final multilayer devices. It is the object of this study to investigate the microwave properties of low-melting ZnO-B_2O_3-SiO_2, BaO-B_2O_3-SiO_2, and PbO-B_2O_3-SiO_2 glasses. The parallel plate dielectric resonator rod method was employed for measurements of relative dielectric constants, quality factors, and temperature coefficients of frequency in the microwave frequency range. A thermo-mechanical analyzer was used to determine deformation temperatures of glasses. Properties of these three glass systems are chiefly determined by the amount of structural modifier oxides (ZnO, BaO, and PbO) and the ionic size of the modifying cations (Zn~(2+), Ba~(2+), Pb~(2+)). In contrast, the effect of the ratio of B_2O_3 to SiO_2 is relatively small. The frequency constants of these three glass systems range from 500 to 3400, which are equivalent to tan #delta# of 0.02-0.003 at 10 GHz. The temperature coefficients of frequency range from -3 to -55 ppm/deg C.
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