Effect of Li2O-Na2O-B2O3-SiO2 Sintering Aids on the Structure and Dielectric Properties of BaAl2Si2O8 Ceramics

BaO-Al2O3-SiO2 (BAS)-x%(w/w) Li2O-Na2O-B2O3-SiO2 (LNBS) (x=0, 1, 2, 3, 4) ceramics were prepared by solid state route. The effect of LNBS sintering aids on the microstructure and dielectric properties of BAS system ceramics were studied. Deviation between theoretical and experimental permittivity (epsilon(r)) of BAS was discussed. The results showed that LNBS sintering aids could reduce the sintering temperature from 1 400 to 1 325 degrees C, and the O2- vacancy or Ba2+ were formed by Li+ substituting for Al3+ or Li+ entering into the single four-membered-ring (S4R) to promote the transformation of hexacelsian to celsian of BAS. The density, quality factor (Qf) value, the temperature coefficient of resonant frequency (tau(f)) of BAS-x% LNBS ceramics have been improved by adding moderate LNBS sintering aids. The BAS-1% LNBS sintered at 1 325 degrees C obtained well dielectric properties: Qf= 35 199 GHz, epsilon(r)=6.37 and tau(f)= -1.613x10(-5) degrees C-1.