CHEMICAL REACTIONS AND DIELECTRIC PROPERTIES OF THE BATIO3-LAALO3 AND BATIO3-LAALO3-LATI3/4O3 SYSTEMS

摘要

BaTiO3-LaAlO3 interaction at high temperatures results in formation of (Ba,La)(Ti,Al)O-3 solid solution, BaAl2O4, and Ba2TiO4. The composition of solid solution can be expressed as Ba1-nLanTi1-052nAl0.36nO3 with 0 less than or equal to n less than or equal to 0.27. Formation of secondary phases BaAl2O4 and Ba2TiO4 which form due to unequal solubility of La3+ and Al3+ ions into the perovskite BaTiO3 lattice can be prevented by the addition of La2O3 and TiO2 in ratio 2:3, i.e., as LaTi3/4O4. Incorporation of La and Al into BaTiO3 strongly decreases the Curie temperature of BaTiO3, approximate to 35 K/mol% LaAlO3 added. (Ba,La)(Ti,Al)O-3 solid solution ceramics exhibit relatively low permittivities at room temperature (734-129) and very low dielectric losses, tan delta<5 x 10(-4) measured at 1 MHz. The temperature stability of permittivity increases with LaTi3/4O3 as well with LaAlO3 concentration. (C) 1997 Academic Press. [References: 20]