Effects of the Susceptor Dielectric Properties on the Microwave Sintering of Alumina

Microwave sintering of alumina has been carried out using

SiC

and Y‐

ZrO

2
based susceptors. The microstructure of the sintered samples has been rigorously compared and correlated to the heating behaviour of the susceptor used. It was found that the nature of the susceptor highly influences the sintering behaviour of alumina. The results show that at high temperatures, the electrical conductivity of the

SiC

susceptor tends to screen the incident electric field, thus resulting in a surface heating of the alumina sample material. When using

ZrO

2
susceptor, the microstructure analysis of the sintered alumina samples reveals a volumetric heating, which is a signature of the microwave dielectric loss mechanism. This could be explained by the lower

ZrO

2
electrical conductivity compared to the

SiC

one. The simulation results confirm this behaviour, particularly showing that in the presence of

ZrO

2
, the intensity of the electric field within the sample is higher than the one when

SiC

susceptor is used. Basically, the results of the simulation data are in good agreement with our experimental results. Although the

SiC

based susceptor is usually used in the microwave heating of materials, the

ZrO

2
based susceptor presents numerous advantages over the

SiC

one, especially in term of direct microwave heating contributions.