Microstructures and Microwave Dielectric Characteristics of Ba6 − 3x (Sm1 − y La y )8 + 2x Ti18O54 Solid Solutions (x = 2/3 and 0.75)

Ba_{6 – 3x}(Sm_{1 – y}La_y)_{8 + 2x} Ti₁₈O₅₄ solid solutions were prepared and characterized. For x = 2/3, tungsten bronze type solid solutions were observed in the entire range of y = 0–1. While, La substitution for Sm will change the phase constitution in Ba_{6 – 3x}Sm_{8 + 2x} Ti₁₈O₅₄ ceramics with x = 0.75. Though the single phase solid solutions were observed for the compositions at the vicinity of the end-members, La₄Ti₉O₂₄ secondary phase was detected for the compositions of y = 0.3–0.8. For x = 2/3, the dielectric constant increased continuously with increasing y, and the Q · f value increased slightly at first then decreased. The dielectric constant had more complex change with increasing y for the situation of x = 0.75 where Q · f value decreased continuously. In both cases, the temperature coefficient of resonant frequency varied from negative to positive with increasing y.