No abstract

The low-temperature sintering of (Ba 0.6 Sr 0.4 ) (Ti 0.94 Cu 0.06 )O 3 (BSTC) ceramics was investigated by conventional ceramics processing using a B 2 O 3 sintering aid, and the dielectric properties and microstructures of the ceramics were examined. BSTC powders without B 2 O 3 could not be fully densified at sintering temperatures lower than 1150 • C. However, the addition of B 2 O 3 markedly enhanced the sinterbility of BSTC powders, and the sintering temperature decreased from 1150 to 980 • C. This may be due to the promotion of liquid-phase sintering. The 3 at.% B 2 O 3 -doped BSTC ceramics sintered at 980 • C for 2 h exhibited a high density of 5.48 g/cm 3 . Transmission electron microscopy examination indicated that there are two kinds of secondary phases produced in BSTC ceramics during B 2 O 3 addition; one is BaTi(BO 3 ) 2 with rhombohedral structure, and the other is Ba 4 Ti 12 O 27 with monoclinic structure. The BSTC ceramics with 3 at.% B 2 O 3 sintered at 980 • C in air for 2 h exhibited a maximum permittivity, ε max = 1216, and a bulk density > 96% of theoretical density.

This study investigates the effect of B 2 O 3 on the sintering behaviour, dielectric properties and microstructure of Ba 0.6 Sr 0.4 TiO 3 + 0.6% CuO (BSTC) ceramics. Ceramics were sintered in air at temperatures ranging from 900 to 1150°C. There are two kinds of secondary phases produced in BSTC ceramics during B 2 O 3 addition; one is BaCuB 2 O 5 with a melting point of approximately 850°C, and the other is BaTi(BO 3 ) 2 with a melting point of ³749°C. The amount of secondary phase present was seen to increase as the amount of B 2 O 3 additives increased. The BSTC ceramics with 1 mass % B 2 O 3 sintered at 1000°C in air for 2 hours exhibited a maximum permittivity, ¾ max = 1826, and a bulk density >95% of theoretical density. Moreover, 0.5 mass % B 2 O 3 doped BSTC sintered at 1000°C exhibits a maximum permittivity, ¾ max = 2100, and a bulk density >92% of theoretical density.