Temperature Stability of Li₂TiO₃‐Zn₂SiO₄ Microwave Dielectric Ceramics

Abstract

In this work, microstructure, composition, and microwave dielectric properties of nominal compositions (1‐x)Li2TiO3‐xZn2SiO4 (x=0.1, 0.2, 0.3, 0.4), which were prepared by conventional solid‐state ceramic route, have been investigated. Li2TiO3 and Zn2SiO4 reacted to form Li2ZnSiO4 and Zn2Ti3O8, where Zn2Ti3O8 is formed during Zn2TiO4 cooling. The microwave dielectric properties of samples are mainly affected by the characteristics and relative content of crystal phase and densification. With the increase of x, the relative dielectric constant (ϵr) decreases gradually. The quality factor (Qf) value increases at first, reaches the maximum value at x=0.2, and then decreases. The temperature coefficient of resonance frequency (τf) value has a sharp decrease due to the increase of Li2ZnSiO4. A near zero τf of about −2.0 ppm/°C was obtained in 0.8Li2TiO3–0.2Zn2SiO4 ceramic sintered at 1150 °C for 4 h with ϵr value of 17.67, Qf value of 19,600 GHz. Thus, it could be a candidate for microwave devices.

Influence of sintering characteristics and structural properties on the microwave dielectric properties of non-stoichiometric Ca3Mn2+xGe3O12+δ (x = 0–0.2) ceramics

“…The Q × f value is influenced by both internal and external factors. 19 External factors are mainly related to the densities, phase compositions, grain sizes, and packing densities of the samples. 20–24 The cell parameters of the samples were determined through Rietveld refinement, and the atomic packing density was calculated as follows: 22–25 where r Ca (1.12 Å), r Mn (0.58 Å), r Ge (0.39 Å), and r O (1.42 Å) denote the effective ionic radii of Ca, Mn, Ge, and O, respectively, and Z is the number of chemical formula units in the unit cell.…”

“…where R ij is the bond valence parameter, 43 d ij is the bond length, and b is a constant (0.37 Å). The effect of lattice anharmonic vibration on dielectric loss can be represented by the damped resonance model: 44 tan d = go/o T 2 (19) where o and g are the frequency of the applied electric field and the damping constant, respectively, and o T is the resonance frequency of the damped vibration (eqn ( 19)). Reducing the damping of nonsimple harmonic vibrations can increase the value of Q Â f. The bond valence (B2.81) of the sintered CM 2.1 G sample at 1180 1C is the closest to the ionic valence state of Mn.…”

“…The Q Â f value is influenced by both internal and external factors. 19 External factors are mainly related to the densities, phase compositions, grain sizes, and packing densities of the samples. [20][21][22][23][24] The cell parameters of the samples were determined through Rietveld refinement, and the atomic packing density was calculated as follows: [22][23][24][25] Packing fraction ¼…”