PREPARATION OF SR BETA-ALUMINA IONIC CONDUCTORS AND THEIR AC-IMPEDANCE MEASUREMENTS

beta-alumina type ionic conductors were synthesized in the SrO-MgO-Al2 O3 system by a direct sintering method and their electrical conductivi ty was measured at 873 to 1373 K by an a.c. impedance method in order to apply the beta-alumina to solid electrolyte of a gas sensor at high temperatures. Sr beta-aluminas in a single phase were obtained in the composition range of SrO : MgO : Al2O3 =1 : 1 : 4.8-5.2. The bulk and grain boundary conductivities were separated from the total conductiv ity at SrO : MgO : Al2O3=1 : 1 : 4.8 and 1 : 1 : 5.0. The bulk conduct ivity of the Sr beta-alumina was around 6.7 x 10(-3) S.m(-1) at 1373 K .