Structural Evolution and Microwave Dielectric Properties of Li(3−3x)M4xNb(1−x)O4 (M=Mg,Zn; 0≤x≤0.9)

Abstract

Structural evolution of Li(3−3x)M4xNb(1−x)O4 (M=Mg,Zn; 0≤x≤0.9) and microwave dielectric properties of Li(3−3x)Mg4xNb(1−x)O4 have been studied by X‐ray diffraction, scanning electron microscopy, Raman spectra, infrared reflectivity (IR) fitting, and microwave resonant measurement in this work. The crystal symmetry changed from the ordered cubic Li3NbO4 (I‐43m, x=0) into disordered cubic phase (Fm3m) when 0.01≤x<1/3 for the Mg‐doped samples. An intermediate compound of Li3Mg2NbO6 (SG:Fddd) with orthorhombic structure formed at x=1/3 composition. MgO secondary phase appeared in addition to Li3Mg2NbO6 phase in the x>1/3 compositions, and its content increased with the further increase of x. Short‐range cation ordering was confirmed to be present in the cubic phase by Raman analysis. Mixture of Li3NbO4 and ZnO phases was observed in the whole composition range for the ZnO‐added samples. For the Mg‐doped samples, the dielectric constant increased slightly with x increasing up to x=1/3 and decreased with the further increase of x. The Q×f value increased greatly with the increasing x and saturated within the composition range of 0.1≤x<1/3. Further increasing x resulted in a decrease in Q×f value. All samples exhibited negative τf value. Minimum τf value of −22 ppm/°C was obtained at x=1/3. The IR reflection spectra of the x=0, 0.2, and 1/3 samples were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. The calculated dielectric constants were in agreement with the experimental ones, whereas, the calculated Q×f values showed a reverse varying trend compared with the experimental data.

Microstructure and microwave dielectric properties of (1−y)Li3NbO4+yLi2TiO3(Li2SnO3) ceramics

“…3 shows the Raman spectra of (1 − y)Li 3 NbO 4 + yLi 2 TiO 3 ceramics. Little change in Raman spectra was observed for the 0.02 ≤ y ≤ 0.2 compositions, which exhibited almost the same spectrum as that of pure Li 3 NbO 4 ceramic [9]. The results obtained from Raman analysis for the 0.02 ≤ y ≤ 0.2 compositions are well consistent with that observed by XRD.…”

“…However three weak broad bands could be observed for the above compositions, which excluded the completely random distribution of ions in those compositions. The weak broad bands in the Raman spectra of y = 0.4 and y = 0.6 compositions can be interpreted as an evidence of short range ordering (SRO), which is agreement with that observed for Li 3 NbO 4 -MgO [9].…”

Li 4 WO 5 : A temperature stable low-firing microwave dielectric ceramic with rock salt structure

“…Among them, some Li-containing compounds with rock salt structure, such as Li 2 TiO 3 and Li 3 NbO 4 , were reported to exhibit a combination of low sintering temperature and excellent microwave dielectric properties [18][19][20]. For example, Li 2 TiO 3 had a permittivity of 22, Q × f value of 63,500 GHz (at 8.6 GHz), and f value of 20.3 ppm/ • C [18].…”

Synthesis of nanosized BaZrO3 from oxalate precursor

“…Special dielectric materials (high dielectric constant and low loss) are used in microelectronics industry in shortand long-range communications [11]. The recent progress in microwave telecommunication, satellite broadcasting, and intelligent transport system has resulted in increasing demand for dielectric resonator antenna which is low loss ceramic pucks used mainly in wireless communication devices [12]. The high dielectric constant and low loss characteristics in BaZrO 3 ceramics make it as a promising material for various microwave applications [13].…”