The effect of crystallization on the stress required for complete constrained sintering of a low-temperature cofirable CaO-B 2 O 3 -SiO 2 glass-ceramics has been investigated under uniaxial constant and cyclic loading. As the formation of crystalline phase of wollastonite (CaSiO 3 ) increases, the uniaxial viscosity of the porous glass-ceramics during firing increases. Moreover, the required uniaxial stress to have complete constrained sintering, i.e., zero strain or strain rate at the perpendicular directions, is in the range of 80-180 kPa, which shows no significant dependence on heating rate and firing temperature. The measured data of required stress are close to those calculated using the viscous analogy for the constitutive relationship of a porous sintering compact.

Effects of Ag addition on sintering of a crystallizable CaO‐B2O3‐SiO2 glass have been investigated at 700°–900°C in different atmospheres. With Ag content increasing in the range of 1–10 vol%, the softening point, the densification, the onset crystallization temperature, and the total amount of crystalline phase formed of the crystallizable glass are reduced when fired in air. A bloating phenomenon is observed when the crystallizable CaO‐B2O3‐SiO2 glass doped with 1–10 vol% Ag is fired at 700°–900°C for 1–4 h. Fired in N2 or N2+ 1% H2, however, the above phenomena disappear completely. It is thus believed that the diffusion of Ag into the crystallizable glass, which is caused by the oxidation of Ag in air, is the root cause for the above results observed.

The effects of a liquid-phase-sintering aid, BaCuO 2 -CuO (BCC), on the densification and dielectric properties of BaTiO 3 ceramics have been investigated. The densification temperature of BaTiO 3 is greatly reduced from 1300-1350 C down to 1050 C in the presence of BCC. This is attributed to a chemical reaction taking place at the interface of BCC/BaTiO 3 during firing. The BaTiO 3 dissolves into BCC, forming crystalline phases of BaCuO 2 , CuO, Cu 2 O and Ba 6 Ti 17 O 40 , and this enhances the densification kinetics of BaTiO 3 . For the samples with 2.0-2.5 wt% BCC, a high relative sintered density of >95% is obtained at 1050 C, and the resulting dielectric ceramics have a dielectric constant and dielectric loss in the range of 2200-2400 and <3% at 1 MHz, respectively.