Impact of additives and processing on microstructure and dielectric properties of willemite ceramics for LTCC terahertz applications

Abstract The paper presents the fabrication procedure, microstructure and dielectric properties of the low temperature cofired ceramics (LTCC) based on Zn2SiO4 doped with AlF3, CaB4O7, Li2TiO3 and MgTiO3. The heating microscope studies and differential thermal analysis were used for characterization of the behavior of the green tapes and ceramic samples during heating up to high temperatures. The microstructure and composition were analyzed by scanning electron microscopy, X-ray energy dispersive spectroscopy and XRD method. The dielectric properties were investigated in three frequency regions: 100 Hz-2 MHz, 90-140 GHz and 0.15-3 THz. The developed materials are promising candidates for the LTCC submillimeter wave applications due to a low sintering temperature of 900-980 °C, good compatibility with silver pastes and good dielectric properties – a low dielectric permittivity of 6-6.8, a relatively low dissipation factor of 0.005-0.008 at 1 THz, and a weak temperature dependence of dielectric permittivity.