Comparison of the effect of conventional and microwave sintering on structural and dielectric properties of AlN - CaZrO3 and Y2O3 composite ceramics

Sintering AlN composite ceramics at low temperatures without forming Al2O3 poses is a significant challenge. This investigation demonstrates the comparative studies of conventional and microwave sintering of AlN ceramics with CaZrO3 and Y2O3 additives. In the conventional sintering method, the AlN composites are sintered at 1700 degrees C for 20 h in a powder bed. In contrast, the microwave sintering method, AlN composites are sintered at 1400 degrees C for 30 min in a susceptor bed. Both approaches successfully yield a pure wurtzite AlN structure with space group P6(3)mc with no traces of secondary phase obtained for all pure and additive ceramics, achieving a relative density exceeding 97 % in the ACZ2Y sample. Raman spectroscopy further confirms the wurtzite structure AlN, characterized by six vibrational modes across all sintered composite ceramics. Dielectric properties are assessed over a temperature range of -140 to 200 degrees C and frequencies between 1 and 100 MHz. The optimal composite, ACZ2Y, displays microwave dielectric properties with epsilon(r) similar to 9.94 and tan delta similar to 11.04 x 10(-4) sintered in the conventional sintering and epsilon(r) similar to 9.02 and tan delta similar to 7.34 x 10(-4) in the microwave sintering, respectively. The microwave-sintered ACZ2Y composite also achieves the highest hardness of 1079.51 HV30, attributed to grain size and compactness. Compared to the conventional sintering method, microwave sintered composite exhibited superior dielectric properties, achieving appropriate relative density in short duration and at reduced sintering temperature. As a result, AlN ceramics produced by microwave sintering are excellent choices for electrical and microwave applications.