High Dielectric Constant YIG Ferrites with Low Sintering Temperature

Abstract

Yttrium-Iron-Garnet (YIG) ferrites are widely used in microwave communication systems due to its excellent gyromagnetic properties. However, these YIG materials were normally synthesized under a high sintering temperature (− 1450 °C). In this work, a high dielectric constant YIG ferrite with a formula of Bi_1.4Y_1.3-xCa_0.3+xZr_0.3Sn_xFe_4.5-xO_11.7 was designed and successfully fabricated under a temperature as low as 950 °C, by using the conventional solid-state reaction method. And the effect of Ca-Sn co-substitution on the microstructure, dielectric properties, and magnetic properties were systematically investigated. In the frequency range of 1 MHz–0.5 GHz, the dielectric constant (ε') of all samples showed frequency-independent behavior and abnormally high values (> 30). And the dielectric loss (tanδ) value remained relatively low (10^–3) in this frequency range. However, ε' and tanδ both increased with increasing frequency in the range of 0.5 GHz–1 GHz. Results further indicate that the increase of Ca–Sn co-substitution made the lattice constant increase approximately linearly, while the volume density gradually decreased. An excellent electromagnetic performance of low-temperature sintered YIG ferrite was obtained: 4πM_s = 1843.34Gs, H_c = 2.51Oe, and ΔH = 190Oe. This study indicates that the as-synthesized YIG ferrites are suitable for processing high-performance, miniaturized radio frequency passive devices through LTCC method, and they are promising for microwave communication applications.