Low-temperature co-fired NPO-type ceramic composition for high-frequency capacitor applications

Low-loss dielectrics of the temperature specification NPO are prepared from the system BaTi4O9 containing Zn-B-O glass. It was found that the addition of small amount of glass to BaTi4O9 lowered the sintering temperature of below 950degreesC, allowing high electrical conductivity metallization with Cu. High frequency multilayer ceramic chip capacitors (MLCCs) were fabricated. The copper electrodes, combined with low fire BaTi4O9 give high Qs of up to 100 at GHz frequencies. The degradation mechanisms of dielectric properties in reducing atmosphere have been studied. The investigations of the dielectric properties at low frequency have enabled us to explain the presence of the mobile charge carriers that cause space-charge polarization in low-fired BaTi4O9 samples. Reliability of the compositions with Cu electrodes was also investigated using transmission electron microscopy and X-ray diffraction.