Microwave dielectric high-entropy ceramic Li(Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)GeO4 with stable temperature coefficient for low-temperature cofired ceramic technologies

(Hf0.25Zr0.25Sn0.25Ti0.25)O2 high‐entropy ceramics and their microwave dielectric characteristics

“…The variation tendency of τ f with sintering conditions in the present high‐entropy ceramics should be closely linked with structure, especially the distortion of the oxygen octahedron caused by the joint occupancy of Hf 4+ , Zr 4+ , Sn 4+ , and Ti 4+ cation sites in the [MO 6 ] octahedron, which could lead τ f to be more negative 22,23 . The calculated octahedral distortion (∆ octa ) is defined by Equation (1) 13,23,24 $$\begin{equation}{\rm{\;}}{\Delta _{{\rm{octa}}}}{\rm{ = }}\frac{{\rm{1}}}{{\rm{6}}}\;\sum {\left( {\frac{{{R_{\rm{i}}} - {R_{{\rm{av}}}}}}{{{R_{{\rm{av}}}}}}} \right)^{\rm{2}}}\end{equation}$$…”

“…Recently, so‐called high‐entropy ceramics have been widely investigated to achieve the improved characteristics, where such novel materials are composed of single‐phase structure with at least four cations and/or anions at one site in the crystal 12–15 . It is believed that the high configuration entropy can enhance the simultaneous solubility for more components, which can be used in optimizing specific properties 16 .…”

“…Considering that the dielectric loss is deeply linked with the homogeneity and the limit of high entropy is just a uniform state, high‐entropy ceramics might provide a new approach to modify the microwave dielectric characteristics. Actually, the attempt on high‐entropy microwave dielectric ceramics has been reported in Li(Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 Lu 0.2 )GeO 4 system, where the near‐zero τ f was achieved, but the Qf value was not so high 13 . Therefore, it is worth to further determine the variation tendency of microwave dielectric characteristics in high‐entropy ceramics, and the most important issue is whether the dielectric loss can be modified by introducing high‐entropy compositions or not.…”

Sintering characteristics, phase transitions, and microwave dielectric properties of low-firing [(Na 0.5Bi 0.5) x Bi 1− x ](W x V 1− x )O 4 solid solution ceramics

“…4(b). TCF value is sensitive to changes in the crystal structure of microwave dielectric ceramics, especially to the distortion of the oxygen polyhedron [39][40][41][42]. Thus, ion doping is widely used as an effective way to achieve a wide range of modulation of TCF values.…”

Entropy regulation in LaNbO4-based fergusonite to implement high-temperature phase transition and promising dielectric properties

“…Xie et al reported a giant dielectric constant (~ 320,000 at 642 °C and 100 Hz ) in (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2Ce2O7 high-entropy ceramics with defect fluorite structure [16]. Xiang et al prepared Li(Gd0.2Ho0.2Er0.2Yb0.2Lu0.2)GeO4 microwave dielectric ceramics via high-entropy solid solubility and optimized the microwave dielectric properties (εr = 7.6, Q×f = 11,700 GHz, τf = -7.4 ppm/�) [17]. Liu et al prepared an olivine structured (Mg0.2Ni0.2Zn0.2Co0.2Mn0.2)2SiO4 high-entropy ceramics with the optimal microwave dielectric properties (εr of 8.02, tanδ of 5.1×10 -4 at 14.5 GHz, and τf of -38.2 ppm/�) [18].…”