Crystal structure and microwave dielectric properties of (Mg0.2Ni0.2Zn0.2Co0.2Mn0.2)2SiO4- A novel high-entropy ceramic

Novel (Mg0.2Ni0.2Zn0.2Co0.2Mn0.2)(2)SiO4 (A5SO) high-entropy microwave dielectric ceramics with olivine structure were prepared in the sintering temperature range of 1100 degrees C-1300 degrees C via the solid-phase reaction route. The crystal structure was confirmed by XRD, Raman, and Rietveld refinement. Optimal microwave dielectric properties (epsilon(r) = 8.02, tan delta = 0.00051 at 14.5 GHz, and tau(f) = -38.2 ppm/degrees C) were obtained at the sintering temperature of 1250 degrees C, where a relative density of 95.1% was detected. The complex chemical bonding theory manifests that the epsilon(r) value of A5SO is mainly affected by the ionicity of A-O (A = Mg, Ni, Zn, Co, Mn) bond, while the dielectric loss is affected by both A-O and Si-O lattice energy. The tau(f) value is mainly influenced by the [A(2)O-6] oxygen octahedral distortion (1.8 x 10(-3)). The experimental results of this study provide both theoretical and practical guidance for high-entropy microwave dielectric ceramic applications.