Reaction Sequence and Effects of Calcination and Sintering on Microwave Properties of (Ba,Sr)O‐Sm₂O₃‐TiO₂ Ceramics

Abstract

The reaction sequence of 0.15(Bao.9sSro.os)0. 0.15Sm2o3 * 0.7Ti02 ceramics during heating as well as the effects of calcination and sintering on microwave properties were investigated. Quantitative microscopic analysis was performed to obtain the volume fraction of the phases. It was found that the amount of second phase, especially T i 2 (rutile), greatly affected the temperature coefficient of resonant frequency of the ceramics. The higher the amount of Ti02 phase, the more positive or the less negative the temperature coefficient of resonant frequency. The temperature coefficient of BaO -Smt03*STiOt was calculated using the logarithmic mixing rule to be -30 ppm/OC. The volume fractions of the phases varied with conditions of calcination and sintering. Therefore, by varying calcination and/or sintering temperature, the temperature coefficient of resonant frequency could be adjusted to nearly zero. [

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

“…This is easily explained by our milling process and calcination which allows a different reactivity of the powder to be reached. The latter hypothesis is confirmed by the fact that in our case at 1000~ BaTi40 9 has completely disappeared contrary to what was found by Wu and Chang [6] at the same temperature. The TG analysis performed in air confirms the early decomposition of BaCO 3 ( Fig.…”

“…With our experimental method, the formation of the nonstoichiometric tunnel structure is observed at 1000~ instead of at 1050~ by previous authors [6]. This is easily explained by our milling process and calcination which allows a different reactivity of the powder to be reached.…”

“…This phenomenon already reported by Wu and Chang [6] was attributed to a variation of the TiO2 amount, present in the matrix as a secondary phase. We were unable to confirm their interpretation from our own SEM observations.…”

“…which shows a progressive decrease of Qf from 9300 GHz for composition 1 to 8500 GHz for composition e. From Q values of Ba2TigO2o and TiO 2, 10 000 and 14 600 at 3 GHz, respectively [6], (i.e. Qf 30 000 and 43 800 GHz), one should obtain a lower Qf factor for the well-densified pure bronzoid than for sample 'a' if one postulates that the Qfvalue is related to the amount of each secondary phase.…”

Microwave Dielectric Properties of Ti-Te system Ceramics for Triplexer Filter

“…This phenomenon is similar to sintering density. The dielectric constant is determined by the composition of material and is affected by the size of the grain, pore (ε r =1), and secondary phase [16].…”