【作者】 刘婷；

【导师】 徐业彬；

【作者基本信息】 华中科技大学 ， 物理电子学， 2012， 博士

【摘要】 不同掺杂的铁电陶瓷BST复合材料,可以用来制备随外加电场变化而变化的微波调谐器件,例如：调谐器、滤波器、移相器等。此外,近年来铁电体块材也用来制备高功率移相设备的控制元件和直线对撞机的转换开关。在介质填充加速器结构中,可以用铁电层来做控制元件。在这些设备中使用的陶瓷材料的介电性能要满足一定的参数要求：相对低的介电常数(<500),在电场2-5kV/mm下的调谐率不低于10%-20%,微波范围内有较低的介电损耗(<0.005)。本论文系统地研究了Ba/Sr比、(Mg2TiO4+MgO)含量及Mg2Ti04与MgO比对复合材料BST/Mg2TiO4/MgO的物相结构和低高频介电性能的影响。探讨了La2O3,Zr02,过渡金属氧化物MnCO3和Co(NO)3·6H2O及低熔点材料CuO、Li2CO3和ZnO掺杂对BST/Mg2TiO4/MgO结构及介电性能的影响。降低Ba/Sr比以及加入MgO可以抑制BST/Mg2TiO4中杂质相BaMg6Ti6O19的产生。MnCO3、ZnO和适量的ZrO2掺杂能提高40Ba0.55SrO45TiO3/12Mg2TiO4/48MgO的调谐率和Qxf值。0.5mol%MnCO3掺杂和0.5wt%ZnO掺杂的40Ba0.55Sr0.45TiO3/12Mg2Ti04/48MgO的复合陶瓷的综合性能较好,微波频率下的Qxf值分别为387GHz和470GHz,在10kHz,2kV/mm电场强度下的调谐率分别为12.5%和11.7%。La203掺杂的40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO的复合陶瓷,La203的掺杂含量高于2wt%后,调谐率随着外加电场强度的增加反常增加,调谐率为负值,继续增加La203含量,调谐率的绝对值增加。Li2C03掺杂的BST/Mg2TiO4/Mg0的复合陶瓷的烧结温度明显降低,优化的烧结温度从1370℃降低到1250℃。改变制备工艺对Zr02掺杂的40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO的复合陶瓷的性能没有明显的影响。本论文研究表明,MnCO3、ZnO和适量的Zr02掺杂能有效地提高40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO的调谐率和Qxf值,是很有希望的微波调谐材料。本论文由国家自然科学基金(项目批准号：10975055)资助。更多还原

【Abstract】 Ferroelectric ceramics of BST solid solutions with various additives are the basic ceramic materials to design microwave devices operated by the electric field, namely modulators, filters, phase shifters, and other. Moreover, an interest appeared recently towards the use of bulk ferroelectrics as control elements of high-power phase-shifters and switches for linear colliders. Ferroelectric layers can be also used as control elements for accelerating structures with dielectric loading. The main requirement for the electrical properties of ceramic materials to be used in such devices is a combination of relatively low dielectric constant is below500at the electric field tunability not worse than10-20%(electric field magnitude (2-5)kV/mm) and low dielectric losses at the microwaverange (tan δ≤0.005).The effect of the proportion of Ba/Sr, BST and (Mg2TiO4+MgO), Mg2Ti04and MgO on the dielectric properties of BST/Mg2TiO4/MgO were studied. The effect of La2O3, ZrO2, MnCO3, Co(NO)3·6H2O, CuO, Li2CO3and ZnO doping on the phase structure and dielectric properties of BST/Mg2TiO4/MgO were studied. The impurity phase BaMg6Ti6O19disappeared with reducing the proportion of Ba/Sr or MgO doping.MnCO3, ZnO and a small amount of ZrO2doping can increase the Qxf value and tunability of40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO ceramics.0.5mol%MnCO3and0.5wt%ZnO doped40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO ceramics show better dielectric properties:the dielectric constant were87.1and131.2at microwave frequency, the Qxf value were387GHz and470GHz and the tunability at2kV/mm were12.5%and11.7%, respectively. With La2O3content exceeding2wt%, the tunabity of40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO ceramics abnormal increases with the increase of electric fields. The tunabity is a negative value. With the increase of La2O3content, the absolute value of tunabity increases. Li2CO3doping can reduce the sintering temperature of BST/Mg2Ti04/MgO ceramics from1370℃to1250℃The preparation technology has no obvious effect on the dielectric properties of ZrO2doped40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO ceramics.Compared with the40Ba0.55Sr0.45TiO3/12Mg2TiO4/48MgO ceramics, MnCO3, ZnO and a small amount of ZrO2doping can increase the Qxf value and tunability and the composite ceramics are promising materials for tunable microwave application.The thesis is supported by Natural Science Foundation of China under grant No.10975055.更多还原