Microwave Dielectric Properties of Ca_0.8Sr_0.2TiO₃–Li_0.5Nd_0.5TiO₃ Ceramics with Near-Zero Temperature Coefficient of Resonant Frequency

Abstract

The microstructure and microwave dielectric properties of (1 À x)Ca 0:8 Sr 0:2 TiO 3 -xLi 0:5 Nd 0:5 TiO 3 (x ¼ 0 {1:0) were investigated. X-ray diffraction and scanning electron microscopy results show that all samples exhibit a single perovskite structure and a dense microstructure. The order of A-site cations was observed in the structure of samples with x ! 0:80 in the X-ray diffraction pattern. The dielectric constant decreased with an increase in x. The quality factor first decreased with an increase in x and then increased slightly with a further increase in x. The temperature coefficient of resonant frequency decreased from high positive values to negative values as x increased. A near-zero temperature coefficient of resonant frequency (À2:75 ppm/ C) was obtained at x ¼ 0:87. Optimized microwave dielectric properties were estimated to be (" r ¼ 111:6; Q Â f ¼ 2013 GHz; f ¼ À2:75 ppm/ C) at x ¼ 0:87.

Determining the Quality Factor of Dielectric Ceramic Mixtures with Dielectric Constants in the Microwave Frequency Range

“…Otherwise, the mixed material will be a single phase solid solution 4,5,17–24 . In previous work, the solid solution was treated as a two-phase composite 16,17,20–24 , where the dielectric constant can be derived from the Maxwell-Wagner equation 7–9,25,26 where V represents the volume molar ratio of the second material, ε r is the dielectric constant of the composite, ε r 1 and ε r 2 are the dielectric constants of the two ceramics, respectively. By using a parallel or serial capacitor model, the parameter k in equation (1) corresponds to +1 and −1, individually 7 .…”

High dielectric constant and low loss microwave dielectric ceramics of (1 &minus; <i>y</i>)(Mg_0.95Co_0.05)₂(Ti_0.95Sn_0.05)O₄&ndash;<i>y</i>(Ca_0.61Nd_0.8/3)TiO₃ for microwave applications

“…Figure 7 shows the¸f values of the (1 ¹ y)MCTSyCNT ceramics sintered at various sintering temperatures. The temperature coefficient of resonant frequency (¸f ) 24)30) is known to be governed by the composition, the additives, and the second phase of the material. This implies that a near zero¸f value can be achieved by tuning the amount of CNT content.…”

Low loss dielectric material system of (1 &minus; <i>x</i>)(Mg_0.95Co_0.05)₂(Ti_0.95Sn_0.05)O₄&ndash;<i>x</i>(Ca_0.8Sm_0.4/3)TiO₃ at microwave frequency with a near-zero temperature coefficient of the resonant frequency

“…Figure 8 shows the¸f values of the (1 ¹ x)MCTSxCST ceramics sintered at various sintering temperatures. The temperature coefficient of resonant frequency (¸f ) 25)31) is known to be governed by the composition, the additives, and the second phase of the material. Because the¸f values of MCTS and CST are ¹46 and +400 ppm/°C, respectively, increasing CST content makes the¸f value more positive.…”