Influences of substituting of (Ni_1/3Nb_2/3)⁴⁺for Ti⁴⁺on the phase compositions, microstructures, and dielectric properties of Li₂Zn[Ti_1−x(Ni_1/3Nb_2/3)_x]₃O₈(0 ≤x≤ 0.3) microwave ceramics

Abstract

Complex ions substitution is gaining more attention as an appealing method of modifying the structure and performance of microwave ceramics. In this work, Li2Zn[Ti1-x(Ni1/3Nb2/3)x]3O8 (LZTNNx, 0 ≤ x ≤ 0.3) ceramics were designed based on complex ions substitution strategy, following the substitution rule of radius and valence to investigate the 2 / 41 relationships between phase composition (containing oxygen vacancies and Ti 3+ ions), microstructure, and microwave dielectric characteristics of LZTNNx ceramics. The samples maintained a single Li2ZnTi3O8 solid solution phase as x ≤ 0.2 whereas the x = 0.3 sample produced a secondary phase with LiNbO3 structure. The appropriate amount of (Ni1/3Nb2/3) 4+ substitution could slightly improve the densification of LZTNNx ceramics due to the formation of Li2ZnTi3O8 solid solution accompanied by a decrease in average grain size. The presence of a new A1g Raman active band at about 848 cm -1 indicated that the local symmetry changed, affecting the atomic interactions of LZTNNx ceramics. The variation in dielectric constant (εr) was closely related to molar volume ionic polarizability, and the temperature coefficient of resonant frequency (τf) was related to the bond valence of Ti. The increase in density, the absences of Ti 3+ ions and oxygen vacancies, and the reduction in damping behavior were responsible for decreased dielectric loss. The LZTNN0.2 ceramic sintered at 1120 o C exhibited favorable microwave dielectric properties: εr = 22.13, quality factor (Q×f) = 97350 GHz, and τf = −18.6 ppm/ o C, which might be a promising candidate for wireless communication applications in highly selective electronics.

Low-permittivity LiLn(PO 3) 4 (Ln = La, Sm, Eu) dielectric ceramics for microwave/millimeter-wave communication

“…Massive MIMO technology, as a crucial solution for 5G and 6G networks, has received widespread attention and has greatly increased the demand for RF devices. Microwave dielectric ceramics, as the key materials of RF devices, have been proposed with new requirements, particularly for low permittivity and high quality factor (Q•f), to reduce signal delay and enhance frequency selectivity [1,2]. Moreover, a low sintering temperature is recommended, which is beneficial for energy conservation and reduces greenhouse gas production [3].…”