Densification and sintering viscosity of low-temperature co-fired ceramics

In this paper, we present sintering and uniaxial viscosity data of three commercial low-temperature co-sintered ceramic systems, i.e., DuPont 951Tape (DU), Heraeus CT2000 (CT), and Ferro A6M (FE), measured by cyclic loading dilatometry. The viscosity initially decreases with temperature, changes little during the intermediate stage, and increases towards the end of densification. The viscosity increases sharply beyond the onset of crystallization. At slower heating rates, the viscosity increases at lower temperature, because of densification and crystallization. The isothermal viscosity data range from 0.1 to 100 GPa · s between 73% and 95% density. Ceramic particle-filled glasses show a higher isothermal viscosity compared with pure glass system, i.e., FE. From master viscosity curves based on isothermal data, the activation energies for viscous flow were ∼375 ± 30 and 450±10 kJ/mol for DU and FE, respectively. These energies are comparable to values obtained from the master sintering curve approach.