Influence of calcination, sintering and composition upon microwave properties of the Ba6−xSm8+2x/3Ti18O54-type oxide

Abstract

Dielectric ceramic compositions for microwave applications belonging to the (BaO) (Sm203) (Ti02) ternary phase diagram were studied. Calcination, sintering, microwave properties and influence of secondary phases were investigated. By varying composition and/or sintering process, a high dielectric constant with low dielectric losses and modulable negative or positive temperature coefficient of the resonant frequency can be reach.

Densification, microstructural evolution and dielectric properties of Ba6−3x(Sm1−yNdy)8+2xTi18O54 microwave ceramics

“…The density increases considerably with the sintering temperature up to 1300 • C, then, levels off above this temperature. The trend of densification curves are consistent with those reported by Laffez et al 26,28 and Ohsato et al 23 Comparing the densification results for y = 0, 0.5, and 1.0 (corresponding to Ba 6 − 3x Sm 8 + 2x Ti 18 O 54 , Ba 6 − 3x (Sm 0.5 Nd 0.5 ) 9 Ti 18 O 54 , and Ba 6 − 3x Nd 8 + 2x Ti 18 O 54 , respectively) shown in Fig. 1, the ceramics with y = 0 [Ba 6 − 3x Sm 8 + 2x Ti 18 O 54 ] generally has a higher densification, and ceramics with y = 1.0 [Ba 6 − 3x Nd 8 + 2x Ti 18 O 54 ] are inferior to the others.…”

Microstructure and dielectric properties of amorphous BaSm2Ti4O12 thin films for MIM capacitor

“…According to previous works, ST ceramic is formed when the sintering temperature of the specimen with the nominal composition of BST is lower than 1150 • C. 16 On the other hand, when the sintering temperature of the specimen exceeds 1150 • C, BST ceramic is formed. 17 Therefore, ST phase is considered to be a low temperature phase of BST ceramics, which is formed when the sintering temperature is not high enough to sinter the BST phase. These results can be used to explain the phase changes, which occurred in the BST films with respect to the growth temperature.…”

Effect of B2O3 Nano-Coating on the Sintering Behaviors and Electrical Microwave Properties of Ba(Nd2 ? xSmx)Ti4O12 Ceramics

“…A sintering temperature of 1350-1370 • C is needed to obtain a ceramic disc with good dielectric properties of k = 105 and Q = 1000 at 1 MHz, however, the temperature coefficient of resonant frequency (τ f ) is very high (−104 ppm/ • C). Laffez [5] sintered BaO-(Nd 2 O 3 , Sm 2 O 3 )-TiO 2 system at 1400 • C and obtained a k of 74 to 81, a Q × f of up to 9000 GHz at 3 GHz, and a τ f of around +9 ppm/ • C. They found that addition of 1 or 2 wt% WO 3 , MnO 2 , and CaO to two compositions of the BaO-(Nd 2 O 3 , Sm 2 O 3 )-TiO 2 system densified ceramics and improved the microwave properties. The WO 3 and MnO doped ceramics show a large dielectric constant, accompanied second phase and lower Q × f value, however, the sintering temperatures are above 1350 • C.…”