Effect of annealing time on structural and microwave dielectric characteristics of Li₂ZnTi₃O₈ ceramics

Abstract

In the present work, the Li 2 ZnTi 3 O 8 ceramics were prepared via the solid-state reaction method, afterward annealed at 800°C in a time variation from 4 to 20 h. The ordering, microstructures and dielectric properties were investigated using x-ray diffraction, scanning electron microscopy, network analyzer, and Raman spectroscopy. The most significant enhancement of quality factor is obtained in the sample annealed for 20 h, while the dielectric constant and temperature coefficient of resonant frequency change slightly. This result mainly attributes to the enhancement of ordering, which could be related to the increase in the Zn-O bond strength in ZnO 4 tetrahedra. Meanwhile, the full-width at half-maximum of A 1g mode decreased with higher annealing time, which suggested less variation in the Zn-O bond length and a higher degree of ordering. The best combination of microwave dielectric characteristic is obtained in the sample annealed at 800°C for 20 h: Q Â f 5 112,400 GHz, e r 5 24.500, and s f 5 À11 ppm/°C.

Study on structure, microstructure and microwave dielectric characteristics of CaV2O6 and (Ca0.95M0.05)V2O6 (M=Zn, Ba) ceramics

“…Therefore, the structural features, included ordering and disordering, can effectively control the intrinsic losses of the dielectric. Through the following equation, the loss tangent (tan δ = 1/Q × f ) of a dielectric is related to the damping factor ( γ ):where ω T 2 is the resonant frequency of the optical mode of the lattice vibration . This equation reveals that the increase in the damping factor due to reduction of the cation ordering of the crystal structure causes an increase in loss tangent.…”

“…where ω T 2 is the resonant frequency of the optical mode of the lattice vibration. 33 This equation reveals that the increase in the damping factor due to reduction of the cation ordering of the crystal structure causes an increase in loss tangent. Looking at the CZV graph, it can be seen that with increasing the sintering temperature the quality factor enhanced to a maximum value of almost 53 000 GHz at 650°C before dropping with further temperature.…”