Measurement of Viscosity of Densifying Glass‐Based Systems by Isothermal Cyclic Loading Dilatometry

This study describes the isothermal cyclic loading dilatometry (ICLD) technique to measure the viscosity of glass‐based materials. We demonstrate its merit relative to constant‐load techniques in minimizing the stress history effects (changes in shrinkage anisotropy and sample microstructure) that arise due to the application of an external load. A constant‐load test overestimates the viscosity by an order of magnitude compared with a cyclic load test. To obtain accurate viscosity data, maximum loading rates and longer unloading periods are desirable as they reduce effects of shrinkage anisotropy on viscosity values. Representative data for a low‐temperature cofired ceramic (LTCC) material are reported. Nonparametric statistical tests revealed insignificant differences between the viscosity data sets at 5% significance level and thus indicate good reproducibility of the testing methodology.