Investigation on phase structure, spectral characteristics, microstructure and microwave dielectric properties of Li2Zn[Ti1-x(Co1/3Nb2/3)x]3O8 (0.0 ≤ x ≤ 0.4) ceramics.

In this paper, a series of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 (0.0 ≤ x ≤ 0.4) ceramics were prepared via the conventional solid-state method. The influences of (Co 1/3 Nb 2/3)4+ complex ions on the phase composition, spectral characteristics, microstructure, and microwave dielectric properties of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 ceramics were studied systematically. XRD analysis accompanied with Rietveld refinements showed that pure Li 2 ZnTi 3 O 8 solid solution ceramics with the cubic spinel structure were obtained at x = 0.2–0.4. New Raman-active mode of about 858 cm−1 should be attributed to the vibrations of NbO 6 due to the high bond energy of Nb–O bonds, exerting a certain impact on the structure and performance of Li 2 Zn[Ti 1- x (Co 1/3 Nb 2/3) x ] 3 O 8 ceramics. XPS results indicated that Nb5+ ion donor suppressed the deoxidation process and therefore resulted in the disappearance of Ti3+ ion and oxygen vacancy. The downward trend variation in the ε r value with the increase of (Co 1/3 Nb 2/3)4+ content could be explained by the presence of "compressed" cations and "rattling" cations effect. In addition, the Q × f of the current ceramics was closely dependent on relative density, grain size, FWHM, and oxygen vacancy. Good combined microwave dielectric properties of ε r = 24.5, Q × f = 91,250 GHz, and τ f = −16.8 ppm/°C were achieved for the Li 2 Zn[Ti 0.8 (Co 1/3 Nb 2/3) 0.2 ] 3 O 8 ceramic sintered at 1120 °C. High quality factor gives evidence that the Li 2 Zn[Ti 0.8 (Co 1/3 Nb 2/3) 0.2 ] 3 O 8 ceramic is an appealing candidate for highly selective microwave devices. [ABSTRACT FROM AUTHOR]