科研之友
微信
新浪微博
Facebook
分享链接
摘要
The structure and microstructure of the Ca1-x(La0.5Na0.5)(x)WO4 (0.1 <= x <= 1.0) ceramics were investigated using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) method. The microwave dielectric properties of the ceramics were studied with a network analyzer at the frequency of about 10-14 GHz. Continuous solid solutions Ca1-x(La0.5Na0.5)(x)WO4 (0.1 <= x <= 1.0) with Scheelite structure (space group: I4(1)/a) could be densified at 850 degrees C/2 h. The dielectric permittivity increased slightly with the increase in substitution amount. The Q x f value decreased with the increase of x up to x = 0.5, and then increased with further increase of x. The Q x f value increased when the sintering temperature increased from 850 to 950 degrees C for the x < 0.5 compositions, whereas it decreased with the increase in sintering temperature for the x > 0.5 compositions. The tau(f) value changed a little with the variation of x. All samples exhibited negative tau(f) values. Addition of 30 mol% TiO2 to the x = 0.9 composition improved the tau(f) to -9.3 ppm/degrees C with epsilon(r) = 14.4 and Q x f = 14,255 GHz after sintering at 850 degrees C/2 h. The chemical compatibility of Ca-0.1(La0.5Na0.5)(0.9)WO4 + 30 mol% TiO2 composite with silver (Ag) powders was also investigated. The composite showed inert behavior with Ag when cofired at 875 degrees C for 2 h. However small amount of Na0.86WO3 impurity phase was detected in the co-fired specimen.
