Influences of alkali oxides on crystallization and dielectric properties of anorthite-based low temperature dielectrics

The influences of alkali oxides as glass constituents for producing LTCC (Low Temperature Co-fired Ceramics) materials were investigated in terms of variations in physical and dielectric parameters. The LTCC materials were based on typical calcium zinc aluminoborosilicate glasses containing 1-3.5 mol % alkali oxides such as K2O, Na2O and Li2O. All samples were prepared in the same experimental condition, i.e., the ratio of glass/filler and the final firing temperature of 850 degrees C. Densification and crystallization behavior strongly depended on the type and amount of alkali oxides used. For example, crystallization peaks in the DTA curves tended to shift towards the lower temperature region by increasing the content of Na2O and K2O. Specifically, the effect of Li2O was distinct in determining the crystallization behavior and subsequent dielectric properties of the LTCC system. Dielectric constant was measured as values of 7.18-7.78 but dielectric loss was significantly degraded specifically with the addition of 3 mol% Li2O. (C) 2008 The Ceramic Society of Japan. All rights reserved.