Mn掺杂BaTi_4O_9陶瓷结构和介电性能

用电子陶瓷工艺制备主晶相为BaTi4O9(BT4)的介电陶瓷 ,研究用锰掺杂的BaTi4O9陶瓷的结构和介电性能。XRD研究表明BaTi4O9属正交晶系 ,空间群Pmmn ,晶格常数为a =1.45 3nm ,b =0 .3 79nm ,c=0 .62 9nm ,每个原胞有两个分子 ,钛原子位于变形的氧八面体之中。这种氧八面体的极化类似于或大于在BaTiO3和PbTiO3铁电相观察到的极化。锰掺杂极大地增强了Q值 ,在 1MHz下测得的Q值为 125 0 0 .而没有掺杂的陶瓷有高的损耗 ,这可能是由于在空气中烧结时形成Ti3+ ,显然锰的作用是在缺陷平衡中作为一种补偿剂 ,依据反应 :Mn3+ +Ti3+ Mn2 + +Ti4+ ,可能有助于Ti4+ 的形成 .BaTi4O9陶瓷具有优良的介电性能 :低介质损耗、中等介电常数和低的介电常数温度系数 .此种陶瓷制造成多层陶瓷电容器开拓了一种新的应用领域 .

STRUCTURE AND DIELECTRIC PROPERTIES OF Mn-DOPED BaTi_4O_9 CERAMIC

A dielectric ceramic, mainly crystalline BaTi 4O 9(BT 4), was prepared using electric_ceramic technology. The structure and the dielectric properties of Mn_doped BaTi 4O 9 ceramic were investigated. X -ray diffraction studies show that BaTi 4O 9 is orthorhombic, space group Pmmn , with a =1.453 nm, b =0.379 nm, c =0.629 nm, with two formula units per unitcell. Titanium atom is indistorted octahedral of oxygen atom. This polarization of the octahedral is similar to or greater in magnitude than that observed in ferroelectric phases of BaTiO 3 and PbTiO 3. Mn dopants greatly enhance the Q factor up to 12 500 at 1 MHz, whereas undoped ceramic indicate high loss perhaps due to the formation of Ti 3+ during the air atmosphere sintering. Mn clearly behave as a compensator in defect equilibria, probably helping to maintain Ti 4+ accordintg to the reaction: Mn 3+ +Ti 3+ Mn 2+ +Ti 4+ . BaTi 4O 9 ceramic possesses an excellent combination of low dielectric loss, moderate dieletric constant and low temperature coefficient of dielectric constant. Its new application has been explored as a multilayer ceramic capacitor(MLCC).