Jae Beom Kim

Dielectric properties of Ca1-xSm2x/3TiO3-Li1/2Ln1/2TiO3 ceramics

The physical and microwave dielectric properties of Ca 1-x Sm 2x/3 TiO 3 -Li 1/2 Ln 1/2 TiO 3 (Ln=Sm, Nd) have been investigated as a function of the degree of Sm substitution (x = 0.0-1.0). As the calcium vacancy concentration increased with increasing Sm substitution, high Q.f values were obtained due to the formation of a superlattice. The Q.f values of the specimens with Nd increased throughout the entire composition range, due to the formation of complete solid solutions, while those of the specimens with Sm increased up to the solid solution limit x = 0.6, and then decreased due to the formation of a secondary phase Sm 2 Ti 2 O 7 . Dielectric constant (K) and temperature coefficient of resonant frequency (TCF) decreased linearly with increasing Sm substitution. In the (1-y)Ca 2/5 Sm 2/5 TiO 3 -yLi 1/2 Sm 1/2 TiO 3 system, the microwave dielectric properties could be controlled by the variation of y. Typical values of K = 95.5, Q.f = 7200 and TCF = Oppm/°C were obtained for 0.67Ca 2/5 Sm 2/5 TiO 3 -0.33Li 1/2 Sm 1/2 TiO 3 .

Effect of BaO/WO3 on the Microwave Loss Quality of Ba(Mg1/3Ta2/3)O3

Effects of BaO/WO3 ratio on the loss quality of complex perovskite Ba(Mg1/3Ta2/3)O3 were investigated as a function of the amount of (1-y)BaO-yWO3 (y=0.56, 0.8) from 0.3 wt.% to 7.0 wt.% at 10 GHz. The specimens with 1.5 wt.% of y=0.56 and/or with 1.0 wt.% of y=0.8 showed a maximum value of loss quality, respectively, and then decreased with an increase of additive content. The increase of loss quality with (1-y)BaO-yWO3, is resulted that the W6+ ions substitution of Ta5+ ions is enhanced the B-site ordering of Ba(Mg1/3Ta2/3)O3. The dielectric constant and temperature coefficient of resonant frequency (TCF) were decreased slightly with additives, which are due to the increase of BaWO4 phase as a secondary phase. The effects of additives on the intrinsic microwave losses of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000 cm-1.