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 MgTiO3-x wt% MgAl2O4 (x = 5, 10, 15, 20) composite ceramics were investigated. MgTiO3 and MgAl2O4 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 oC 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 MgTiO3 is improved by adding MgAl2O4 second phase up to 10 wt% and for more than it, sintered density of the fabricated composite decreased due to higher refractoriness of MgAl2O4 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 MgAl2O4. 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 MgAl2O4 second phase.