Microwave dielectric properties and applications of rare-earth aluminates

Rare-earth aluminates, LnAlO(3) (Ln = Dy, Er, Gd, La, Nd, Pr, Sm, and Y) we re prepared using the mixed oxide method, and their microwave dielectric pr operties were examined at X-band. Most rare-earth aluminates have suitable permittivities and quality factors for applications as dielectric resonator s, but a modification of tau(f) is necessary due to the coefficient's large negative value. When considering dielectric properties and lattice matchin g, YAlO3, rather than LaAlO3, was suggested as a promising substrate materi al for microstrip antennas utilizing high-temperature superconductor thin f ilms. Rare-earth aluminates with a rhombohedral structure exhibited larger permittivities than those with an orthorhombic structure. This difference w as attributed to the difference in ionic size and coordination number. It w as demonstrated that a nonzero magnetic susceptibility of rare-earth alumin ates has an adverse effect on their quality factor. An abrupt variation in the temperature coefficient of permittivity was discussed in terms of oxyge n octrahedra tilting.