The structure and electrical properties of(Na 0.5 Bi 0.5 ) 0.94 Ba 0.06 TiO 3 ceramic doped with 0.5 wt% of MnO were investigated in comparison with those of(Na 0.5 Bi 0.5 ) 0.94 Ba 0.06 TiO 3 ceramic.It was ascertained that the MnO addition did not cause remarkable change in crystal structure and microstructure.The MnO addition mainly displayed a hard effect on the electrical properties,an increase of coercive field(E c )and mechanical quality factor(Q m )together with a decrease of dielectric constant(ε r )and piezoelectric constant(d 33 ).An enhancement of electromechanical coupling factor(k p )with the MnO addition was obtained too.An essential relation between the piezoelectric properties and ferroelectric nature of the ceramics was detected.It was found that the piezoelectric properties of the ceramics highly depended on the corporative contribution of remanent polarization(P r )and coercive field.
La2O3 and SrO-doped CaO-MgO-Nb2O5-TiO2 system ceramics were prepared by solid-state ceramic technique. The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 ceramics can be adjusted by varying the amount of La 3+ or Sr 2+ ions respectively. The replacement of Ca 2+ by La 3+ at A-site of the ceramics increases the quality factor Q value （at 7.6 GHz） as well as the temperature coefficient of resonant frequency τf and decreases the dielectric constant εr and the substitution of Sr 2+ at A-site in this ceramics system exhibits opposite characteristics. The microwave properties of La 3+,Sr 2+-doped CaO-MgO-Nb2O5-TiO2 system ceramics depend on the degree of octahedral distortion inside materials.
