Microstructure and dielectric properties of novel MgTiO3-x wt% MgAl2O4 microwave dielectric composite ceramics

In this work, the microstructure and microwave dielectric properties of novel MgTiO 3 - x wt% MgAl 2 O 4 ( x = 5, 10, 15, 20) composite ceramics were investigated. MgTiO 3 and MgAl 2 O 4 compounds were synthesized by conventional solid-state reaction method and the composites were fabricated by wet mixing, pressing in die and sintering in the temperature range of 1200–1350 o C for 5 h in air. X-ray analysis of the sintered sample proved that no reaction occurred between the two phases during sintering process. The results proved that sinter-ability of MgTiO 3 is improved by adding MgAl 2 O 4 second phase up to 10 wt% and for more than it, sintered density of the fabricated composite decreased due to higher refractoriness of MgAl 2 O 4 phase. Dielectric constant of the fabricated composites decreases from around 16.4 to 15 by increasing the amount of secondary phase from 0 to 20 wt% and nearly follow a linear relation in semi logarithmic scale. The temperature coefficient of resonant frequency became more negative by increasing the amount of used MgAl 2 O 4 . The quality factors values were determined in the range of 140,000–160,700 GHz, reaching the maximum of 160,700 GHz for the composite includes 10 wt% of MgAl 2 O 4 second phase.