Low-Loss Lithium Ferrites for Microwave Latching Applications

Abstract

Two sets of dense kiln‐fired lithium ferrite ceramic bodies with 4πM_s around 3600 and around 2600 G, respectively, have been prepared with low microwave dielectric losses (tan δ < 0.0005) and high remanence ratios (B_r/4πM_s = 0.7). These low dielectric losses were obtained by addition of MnO₂. For samples which were thicker than 0.25 cm, an anneal in an oxygen atmosphere was required. The lower 4πM_s compositions were obtained by substituting titania for part of the iron oxide in the basic lithium ferrite formulation. A number of physical properties were evaluated and the results are presented. These include density 4πM_s and Curie temperature. In addition, properties useful for microwave latching applications such as complex dielectric constant and hysteresis characteristics, i.e., ramanent magnetization and coercive force are presented. The temperature variation of the hysteresis properties for selected compositions is also shown.