Low-temperature preparation and microwave dielectric properties of ZBS glass–Al2O3 composites

Abstract The preparation and microwave dielectric properties of ZnAl 2 O 4 -based glass–ceramic composites were investigated. Using zinc borosilicate (ZBS) glass and Al 2 O 3 , glass–ZnAl 2 O 4 composites with high quality factor was successfully prepared at temperatures below 950 °C. The linear shrinkage for 50 vol% ZBS glass–ZnAl 2 O 4 composite showed a steep increase up to 650 °C and a plateau between 700 °C and 950 °C, implying that one-stage densification process occurred. The crystallization of ZnAl 2 O 4 was observed above 700 °C and an insufficient densification occurred due to the consumption of the glass. As the sintering temperature increased, the quality factor ( Q × f 0 ) showed an increase with an S-type curve whereas the dielectric constant was almost constant. The formation of ZnAl 2 O 4 might correspond to the increase of Q × f 0 ; a high value of 17,757 GHz (1415 at 12.6 GHz) was obtained for the specimen sintered at 900 °C.