Sintering BaTi4O9/Ba2Ti9O20-based ceramics by glass addition

Abstract

After calcining BaCO3 + 4TiO(2) mixed powder at 1150 degrees C for 2 h, BaTi4O9 is the major phase, Ba4Ti13O30 and BaTi5O11 are minor phases. After calcining 2BaCO(3) + 9TiO(2) mixed powder at 1200 degrees C for 10 h, Ba2Ti9O20 is the major phase, BaTi4O9 and BaTi5O11 are the minor phases. The calcining powders are used as the BaTi4O9 and Ba2Ti9O20 precursors. MgO-CaO-SiO2-Al2O3 (MCAS) composite glass powder, fabricated by sol-gel method, is used as the low melting addition to lower the sintering temperatures of BaTi4O9 and Ba2Ti9O20 dielectric. The addition of MCAS glass does not inhibit the residual satellite phases to transform into BaTi4O9 and Ba2Ti9O20. For MCAS-doped BaTi4O9 and Ba2Ti9O20 ceramics the major phases are BaTi4O9 and Ba2Ti9O20, cordierite is observed as minor phase. The temperatures needed to densify the BaTi4O9 and Ba2Ti9O20 ceramics are lowered down with the increase amount of MCAS glass addition. For BaTi4O9 and Ba2Ti9O20 ceramics, both the densities and the dielectric constants (at 1 MHz) increase with the sintering temperature and decrease with the amount of MCAS glass addition. (C) 2000 Elsevier Science Ltd. All rights reserved.