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

The preparation and microwave dielectric properties of ZnAl2O4-based glass-ceramic composites were investigated. Using zinc borosilicate (ZBS) glass and Al2O3, glass-ZnAl2O4 Composites with high quality factor was successfully prepared at temperatures below 950 degrees C. The linear shrinkage for 50 vol% ZBS glass-ZnAl2O4 Composite showed a steep increase up to 650 degrees C and a plateau between 700 degrees C and 950 degrees C, implying that one-stage densification process occurred. The crystallization of ZnAl2O4 was observed above 700 degrees C and an insufficient densification occurred due to the consumption of the glass. As the sintering temperature increased, the quality factor (Q x f(0)) showed an increase with an S-type curve whereas the dielectric constant was almost constant. The formation of ZnAl2O4 might correspond to the increase of Q x f(0); a high value of 17,757 GHz (1415 at 12.6 GHz) was obtained for the specimen sintered at 900 degrees C. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.