Non-destructive evaluation of ceramic porosity using terahertz time-domain spectroscopy

We measured the dielectric constants of alumina ceramic samples with non-destructive THz time-domain spectroscopy. Using an effective medium approximation, we demonstrated that the relative permittivity can be used to evaluate the porous alumina samples, with porosity fractions ranging from 0% to 20% per volume. This result can be used to control sample porosity, a key material parameter related to mechanical strength under compression load, hardness and wear resistance, or thermal stability.