Structure, defects, and microwave dielectric properties of Al-doped and Al/Nd co-doped Ba4Nd9.33Ti18O54 ceramics

Abstract

Low-loss tungsten—bronze microwave dielectric ceramics are dielectric materials with potential application value for miniaturized dielectric filters and antennas in the fifth-generation (5G) communication technology. In this work, a novel Al/Nd co-doping method of Ba4Nd9.33Ti18O54 (BNT) ceramics with a chemical formula of Ba4Nd9.33+z/3Ti18−zAlzO54 (BNT—AN, 0 ≼ z ≼ 2) was proposed to improve the dielectric properties through structural and defect modulation. Together with Al-doped ceramics (Ba4Nd9.33Ti18−zAl4z/3O54, BNT—A, 0 ≼ z ≼ 2) for comparison, the ceramics were prepared by a solid state method. It is found that Al/Nd co-doping method has a significant effect on improving the dielectric properties compared with Al doping. As the doping amount z increased, the relative dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) of the ceramics decreased, and the Q×f values of the ceramics obviously increased when z ≼ 1.5. Excellent microwave dielectric properties of εr = 72.2, Q×f = 16,480 GHz, and τf = +14.3 ppm/°C were achieved in BNT—AN ceramics with z = 1.25. Raman spectroscopy and thermally stimulated depolarization current (TSDC) technique were firstly combined to analyze the structures and defects in microwave dielectric ceramics. It is shown that the improvement on Q×f values was originated from the decrease in the strength of the A-site cation vibration and the concentration of oxygen vacancies $$\text{V}_\text{O}^{^{ \cdot \cdot }}$$, demonstrating the effect and mechanism underlying for structural and defect modulation on the performance improvement of microwave dielectric ceramics.

Structure, far-infrared spectroscopy, microwave dielectric properties, and improved low-temperature sintering characteristics of tri-rutile Mg 0.5Ti 0.5TaO 4 ceramics

“…This phenomenon is attributed to the low bulk density of LMZBS glass frit of ~2.35 g/cm 3 . A similar variation tendency was found for the dielectric constant, illustrating that the bulk density is vital for developing the dielectric constant [30]. Of particular interest is the dielectric constant value for Mg 0.5 Ti 0.5 TaO 4 ceramics doped with 2 wt% LMZBS glass (44.35) is close to that (43.61) of Mg 0.5 Ti 0.5 TaO 4 ceramics when sintered at 1275 .…”

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

“…The structural characterizations by Rietveld refinement are shown in Table 2. Similar to the XRD pattern, the Raman scattering spectrum is the 'fingerprint' of the phase but is more sensitive to the local structural evolution [31]. The effective radius of different rare-earth ions affects the distortion of the [ReO8] oxygen decahedral, and the slight change of the [ReO8] oxygen decahedral will make the [NbO4] oxygen tetrahedra be implicated, resulting in the corresponding change of the vibration of the chemical bond, which is reflected in the subtle change of the Raman vibration peak.…”

Crystal structure, chemical bond characteristics, infrared reflection spectrum, and microwave dielectric properties of Nd 2(Zr 1− x Ti x ) 3(MoO 4) 9 ceramics

“…Refs. [22,23] show that the dielectric loss of the ceramics can be reduced by adding appropriate ions. Feng et al [24] improved the Q•f value by the partial replacement of Zr 4+ by (Al 1/2 Ta 1/2 ) 4+ ions in Ce 2 Zr 3 (MoO 4 ) 9 ceramics.…”