Mg离子掺杂对含锆铋基焦绿石材料介电弛豫性能影响

Effects of Mg^(2+) Doping on Dielectric Relaxation Characteristics of Bismuth-based Pyrochlores Containing Zr

采用固相反应法制备陶瓷(Bi1.5Zn0.5-xMgx)(Zr1.5Nb0.5)O7(BZMZN)(x=0.1、0.2、0.3、0.5),研究Mg2+取代对材料结构、组成、介电性能以及弛豫特性的影响。X射线衍射分析表明,当Mg2+从部分至完全取代Zn2+,均合成了立方焦绿石主晶相结构,并有微量Bi12MgO19相产生。随着Mg2+取代量的增加材料介电常数和介电损耗略有下降。材料在-150℃左右具有明显的介电弛豫特征,对其弛豫过程进行拟合与计算,并结合价键理论探讨了BZMZN系焦绿石的低温介电弛豫机制,这种弛豫源于材料结构中A位离子的不均匀分布及A位离子与O'位离子的本征跃迁过程。

A series of pyrochlore ceramics with formula(Bi1.5Zn0.5-xMgx)(Zr1.5Nb0.5) O7(BZMZN)(x = 0.1,0.2,0.3,0.5) were prepared by the conventional solid-state reaction method.The structure,dielectric properties and relaxation behavior were systematically investigated.The XRD was used to analyze the phase structure,with the partial and complete Mg2 + substitution of Zn2 +,the crystal structure still maintains the cubic pyrochlore structure with a small amount of Bi12MgO19.With increasing amount of Mg2 + substitution,the dielectric constant and dielectric loss decrease slightly.The dielectric relaxation was found in all BZMZN pyrochlores at about-150 ℃.The relaxation behavior was fitted and the relaxation mechanism was further deduced with the bond-valence theory,the relaxation is related to inhomogeneous distribution of A site atoms and the local intrinsic hopping of atoms in the A and O' positions among several local potential minima.