Structure and microwave dielectric properties of B-site deficient double perovskite – Ba[(Mg(1–x)/2Yx/3□x/6)W1/2]O3

The structural stabilities of double perovskite ceramics – Ba[(Mg(1−x)/2Yx/3□x/6)W1/2]O3(0.0≤x≤0.35) have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Raman spectrometry in this paper. The microwave dielectric properties of the ceramics were studied with a network analyzer at the frequency of about 8–11 GHz. The results demonstrate that small amount of Y substitution for Mg (x=0.05) increased the stability of the double perovskite. However, further increase in Y substitution would lead to the increase in BaWO4 impurity phase. Nonrandom distribution of Y3+, Mg2+ and vacancies on 4b-site within a short range scale was observed due to their large cation size and charge differences, although space group Fm-3m was adopted for all compositions. The substitution of Y3+ for Mg2+ increased the dielectric permittivity. The Q×f value was considerably improved by substitution of Y3+ (x=0.05). The temperature coefficient of resonant frequency changed from negative into positive value and near zero τf value could be obtained at x=0.3 composition. Excellent combined microwave dielectric properties with εr=21.9, Q×f= 133,000 GHz, and τf =−2.4 ppm/°C could be obtained at x=0.3 composition.