Lei Yi

Structure and microwave dielectric properties of SrSmAlO4-Sr2TiO4 solid solutions

The structure and microwave dielectric properties of Sr1+xSm1-xAl1-xTixO4 ceramics were determined in the entire composition range of x = 0 ~ 1.0. The single phase solid solutions with K2NiF4 structure were obtained, and the Q × f value decreased with increasing x at first (up to 0.15) and then turned to increase and reached the maximum at x = 0.9. The dielectric constant εr increased from 19.2 to 36.5 and the temperature coefficient of resonant frequency τf ascended monotonously with increasing x. The variation tendency of Q × f value with x reflected the competition result of the interlayer polarization and the structure inhomogeneity. On the other hand, infrared (IR) reflectivity spectra were measured and fitted by means of classical oscillator model simulation. The intrinsic dielectric loss tangent extrapolated from IR range showed a similar changing trend with the measured ones. Moreover, the fitting results offered a detail inside view of the intrinsic factors and the variation of the dielectric loss could be well explained.

Structures and microwave dielectric characteristics of compounds in vicinity of CaNdAlO4 in CaO–Nd2O3–Al2O3 ternary system

Abstract Abstract Single phase ceramics in the vicinity of CaNdAlO4 in CaO–Nd2O3–Al2O3 ternary system, such as ternary oxide compound CaNdAl3O7 and binary oxide compounds NdAlO3, CaAl2O4, Ca3Al2O6 and Ca12Al14O33, were prepared by the standard solid state reaction route. The phases and structure of the ceramics were analysed through X-ray diffraction and scanning electron microscopy. The microwave dielectric characteristics of the ceramics were studied using a network analyser. High Qf values were obtained in CaNdAlO4, CaNdAl3O7, NdAlO3 and CaAl2O4, while the Qf values in Ca3Al2O6 and Ca12Al14O33 were much lower. The best microwave dielectric characteristics (ϵr = 8·9, Qf = 90 800 GHz at ∼9·40 GHz and τf≈−55·2 MK−1) were achieved for CaAl2O4 ceramics sintered at 1425°C in air for 3 h. It could be expected as a promising new candidate for microwave dielectric ceramics. Moreover, the present results showed the direction for modification of CaNdAlO4 microwave dielectric characteristics through composition tailoring.