| Dielectric ceramic and ceramic-ceramic composite materials with high quality factor
(Q) have attracted increasing attention as low loss substrates for microwave and
millimetre-wave applications operating at high temperatures. This review summarizes
dielectric materials, loss mechanisms, temperature dependent behaviour and reported
dielectric properties of oxide ceramics and ceramic-ceramic composites relevant to
substrates requiring low dielectric loss and thermal stability. Recent studies published
since 2015 are critically reviewed. The quality factor-frequency product (Q·f) values are
discussed primarily as indicators of intrinsic dielectric loss rather than as direct
measures of antenna performance. The review highlights recent progress and remaining
challenges in developing ceramic substrates that simultaneously achieve low to
moderate permittivity, low dielectric loss, and reliable high temperature performance. |
