MnO_2掺杂BaTi_4O_9陶瓷微波介电性能研究

采用传统固相反应法合成BaTi_4O_9粉体,复合掺杂质量分数为0~0.16%MnO_2,在空气气氛下常压烧结制备BaTi_4O_9陶瓷。研究了MnO_2对BaTi_4O_9陶瓷的相组成、微观形貌、烧结特性及介电性能的影响。X射线衍射分析和扫描电子显微镜观察表明,Mn完全固溶到BaTi_4O_9陶瓷中;随着MnO_2掺杂量的增加,晶粒更加均匀,BaTi_4O_9陶瓷更加致密,介电常数略微降低,品质因数和谐振频率温度系数先显著提高继而降低;MnO_2掺杂BaTi_4O_9陶瓷发生Ti位取代,高温烧结时在一定程度上抑制了Ti~(4+)还原为Ti~(3+),从而改善BaTi_4O_9陶瓷微波介电性能。在烧结温度1250℃,保温时间4 h,掺杂MnO_2质量分数为0.08%时,BaTi_4O_9陶瓷微波介电性能最优,介电常数(εr)为34.56,品质因数(Q·f,中心频率5 GHz)为49097,谐振频率温度系数(τ_f)为14.997×10~(-6)/℃,相对密度最大,达97%。

Study on microwave dielectric properties of BaTi4O9 ceramics doped by MnO2

Pure and MnO2-doped BaTi4O9 ceramics (0～0.16％ MnO2 by mass) was fabricated by the conventional solid state reaction method, the phase composition, microstructures, and dielectric properties of MnO2-doped BaTi4O9 ceramics were investigated as the functions of MnO2 content by mass. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies show that Mn is completely dissolved into BaTi4O9 ceramics. As the MnO2 content increases, a more uniform grain size distribution is obtained, the relative density is improved, the dielectric constant is slightly reduced, and the quality factor and temperature coefficient increase significantly and then decrease. It can be determined that the dielectric properties of MnO2-doped BaTi4O9 ceramics are improved due to the Ti substitution by Mn which can inhibit Ti4+ to Ti3+ to some extent. The microwave dielectric properties of BaTi4O9 ceramics doped by 0.08％ MnO2 by mass sintered at 1250℃ for 4 h are optimal, thedielectric constant (εr) is 34.56, the quality factor (Q·f) is49097 (the center frequency is 5.08 GHz), the temperature coefficient (τf) is 14.997×10-6/℃, and the relative density is 97％.