Microwave heating (MW) was studied for the sintering of amorphous powders. In comparison to conventional heating (CV), the results show that microwave heating has the potential to substantially accelerate the sintering process and allow for highly densified solidification by eliminating the pores and increasing the shrinkage rate. In the heat treatment to synthesize aluminum borate (Al 18 B₄O 33 ) whiskers from precursors, it was found that microwave heating helps the formation of Al 18 B₄O 33 crystal as well as the decrease of crystallization temperature of Al 18 B₄O 33 to a level significantly lower than the previously reported value of 1050℃.