Influence of MnCO_3 additive on the dielectric properties of BaCuB_2O_5-doped Ba_(4.5)(Nd_(0.7)Sm_(0.3))_9Ti_(18)O_(54) ceramics sintered in a reducing atmosphere

摘要

Sintered in a reducing atmosphere, the dielectric properties of Ba_(4.5)(Nd_(0.7)Sm_(0.3))_9Ti_(18)O_(54) (BNST) ceramics are deteriorated because of the ionized oxygen vacancies and conduction electrons. The feasibility of reduction resistance in BNST ceramics sintered in a reducing atmosphere was investigated in this work. Prompted by the example of BaTiO_3 ceramics used in base-metal electrode multilayer ceramics capacitor, the effects of acceptor dopant MnCO_3 on the microstructure, insulation resistivity (IR) and dielectric properties of BNST ceramics doped with 1 wt% BaCuB_2O_5 (BCB) sintered under a reducing atmosphere of moist N_2-1%H_2 were investigated. Results showed that MnCO_3 effectively rendered BNST-BCB ceramics resistant to reduction. Mn ions completely substituted into the Ti~(4+) site of BNST at ＜1.5 wt% MnCO_3 doping content, whereas secondary phases were formed with increased MnCO_3 addition. Resistivity as high as 10~(12) Ω cm was effectively achieved in ceramics with the addition of ＞1.5 wt% MnCO_3, and the dielectric constant (ε_r) of BNST-BCB was not obviously modified by the presence of additive. Moreover, 2 wt% MnCO_3-doped BNST-1wt% BCB ceramics sintered in a reducing atmosphere exhibited attractive properties with ε_r = 75.1, tanδ = 0.00115, TCC = -42.3 ppm/℃ and IR = 4.56×10~(12)Ωcm.