Correlation between crystal structure and microwave properties of cordierite type dielectric ceramics

Cordierite-based (Mg2Al4Si5O18) dielectric ceramics with a lower dielectric constant would have significant application potential as dielectric resonator and filter materials for future ultra-low-latency millimeter-wave and terahertz communication. Here we successfully synthesised Cordierite based ceramic compositions with substitution of Al and Si sites with chemical dopants to optimise the microwave dielectric properties, such as Q×f value and temperature coefficient. We believe understanding the crystallography information is paramount in order to optimise their electrical properties however, most of the structural characterisation techniques are insensitive to these light chemical elements, i.e. Al and Si. Instead, high-resolution neutron powder diffraction (room temperature), along with full-pattern Rietveld refinement, provides an opportunity to obtain composition-dependent phase transition, lattice information and atomic positions. The results obtain in this study not only underpin the origin of optimised microwave properties from atomic structural perspective but also provide instructive for the design and development of new and improved dielectric ceramics in the future.