Microstructure, shear strength and dielectric properties of a co-fired YIG-MCT composite substrate for circulators

A YIG-MCT composite substrate for circulators with high shear strength and good dielectric properties was prepared by direct co-firing. The Bi 0.3 Y 2.3 Ca 0.4 Zr 0.4 Fe 4.6 O 12 (B-YIG) ceramic acted as the inner core, and the 0.95MgTiO 3 -0.05CaTiO 3 (95MCT) ceramic acted as the outer ring of the co-fired composite substrate. The influence of co-firing temperatures on the phase composition, microstructure, shear strength and dielectric properties of the as-prepared composite substrate was investigated. Moreover, the transition region of the composite substrate, induced by direct cosintering, was deduced. The results show that the optimal co-firing temperature of the composite substrate is 1280 °C. At the co-firing temperature, the obtained composite substrate shows a high shear strength of 64.20 MPa. New phases, such as MgFe 2 O 4 , Y 2 Ti 2 O 7 , and YFeO 3, form in the transition region because of the interface reaction occurring between B-YIG and 95MCT. The synthesized YIG-MCT composite substrate shows a dielectric constant of 19.7 and a dielectric loss of 5.64 × 10 −4 (9 GHz), demonstrating good dielectric properties. The results indicate that YIG-MCT prepared by co-firing technology is a promising composite substrate for circulator applications.