Sintering Behavior, Crystal Structure, and Microwave Dielectric Properties of Li₂Y₉(SiO₄)₆O₂F Ceramics with Near-Zero _f

This study delves into the microwave dielectric properties of Li2Y9(SiO4)(6)O2F ceramics, synthesized using the conventional solid-state method. By employing x-ray diffraction analysis and meticulous data refinement across various temperatures, we unequivocally confirm the hexagonal crystal structure of Li2Y9(SiO4)(6)O2F ceramics. The refined lattice parameters, observed at a sintering temperature of 1275 degrees C, exhibit a = b = 9.33318 & Aring;, c = 6.71725 & Aring;, with a corresponding unit cell volume of V = 506.73529 & Aring;(3). In-depth scrutiny of the microstructure of the ceramics' grains using scanning electron microscopy (SEM) reveals an optimal relative density of 96.2%. Subsequently, the study explores the impact of porosity, packing fraction, relative density, and Si-O bond valence (VSi-O) on the microwave dielectric properties of Li2Y9(SiO4)(6)O2F ceramics. Notably, the Li2Y9(SiO4)(6)O2F ceramic sintered at 1275 degrees C demonstrates superior performance metrics, boasting an epsilon(r) value of 14.28, a Q x f product of 16,760 GHz (at f = 9.4 GHz), and a temperature coefficient of frequency (tau(f)) at 3.14 ppm/degrees C. This comprehensive investigation contributes valuable insights into optimizing the microwave dielectric characteristics of Li2Y9(SiO4)(6)O2F ceramics for potential applications in advanced electronic devices.