A novel low-firing microwave dielectric ceramic LiScO2 with high thermal stability and low loss

In this work, a LiScO 2 microwave dielectric ceramic with high thermal stability was prepared by a conventional solid-state reaction method. X-ray diffraction combined with Rietveld refinement confirms the formation of a single tetragonal phase (space group I 4 1 /amd ) over a sintering temperature range 825–925 °C. The LiScO 2 ceramic sintered at 900 °C exhibits excellent microwave dielectric properties, including a low relative permittivity ( ε r = 14.9), a high quality factor ( Q × f = 59,465 GHz), and a near-zero temperature coefficient of resonant frequency ( τ f = −3.4 ppm/°C). Moreover, LiScO 2 demonstrates good chemical compatibility with Ag electrodes at 900 °C, indicating strong potential for low-temperature co-fired ceramic (LTCC) applications. The high Q × f value is attributed to favorable ionic radius matching between Li + and Sc 3+ , which suppresses cation rattling effect and high packing fraction. And τ f shows a strong dependence on porosity, varying from −54.30 ppm/°C to nearly zero values with increasing sintering temperature. This behavior suggests that porosity is a key extrinsic factor governing τ f . Finally, LiScO 2 is preliminarily demonstrated as a dielectric resonator antenna suitable for 5 G communication.