【作者】 余涛；

【导师】 余洪滔；

【作者基本信息】 西南科技大学 ， 材料科学与工程， 2022， 硕士

【摘要】 无线通讯技术在不断地更迭,5G网络与多种新技术的联合发展对人们当下的生活提供了极大地便利,这离不开基础的材料研发和应用。由介质陶瓷制备的各种通讯相关器件在各个领域得到了广泛的应用,同时也面临着新时代更高要求的挑战。因而,作为基础核心材料,新型微波介质陶瓷的研发和应用受到了更多的关注和重视。本文选择Li₂Mg₃TiO₆体系为基础材料,以固相法分别在其Ti位和Mg位进行了(Al_0.5Nb_0.5)⁴⁺离子和Zn²⁺离子的掺杂置换,并制备了Li₂Mg₃Ti_1-x(Al_0.5Nb_0.5)_xO₆和Li₂(Mg_1-yZn_y)₃Ti_1-x(Al_0.5Nb_0.5)_xO₆介质陶瓷。随后对其添加烧结助剂进行降温烧结制备了Li₂(Mg_1-yZn_y)₃Ti_1-x(Al_0.5Nb_0.5)_xO₆+Ba Cu B₂O₅介质陶瓷。根据掺杂量的多少,本文从陶瓷的致密度,物相变化,晶体结构,键价理论,堆积系数以及烧结动力学等方面对上述陶瓷进行了研究,并获得了其与陶瓷介电性能的一些依赖性。通过固相法在Li₂Mg₃TiO₆的Ti位掺杂置换的Li₂Mg₃Ti_1-x(Al_0.5Nb_0.5)_xO₆介质陶瓷,在实验范围内均为岩盐立方结构的单一物相。通过对其进行P-V-L化学键键价理论的分析以及各类与键性质相关参数的计算发现,(Al_0.5Nb_0.5)⁴⁺掺杂提高了离子极化率,增大了晶格能,化学键价得到提高,热膨胀系数随掺杂量增加而降低,这些改变共同作用改善了Li₂Mg₃TiO₆陶瓷的介电性能,实现了品质因子的提高,介电常数的增加,以及温漂和烧结温度的降低。(Al_0.5Nb_0.5)⁴⁺掺杂量为x=0.09时获得最佳介电性能（1360℃保温4小时,ε_r=13.86,Q×f=141210 GHz,τ_f=-25.9 ppm/℃）。在此基础上,同样采用固相法进一步在其Mg位进行Zn²⁺的掺杂置换。掺杂量低于0.08时,陶瓷为单一晶相,过量掺杂导致杂相生成恶化介电性能,适量的Zn²⁺离子掺杂可以进一步提高综合介电性能并降低烧结温度。当Zn²⁺掺杂量为y=0.08时,在1320℃保温4小时的Li₂(Mg_0.92Zn_0.08)₃Ti_0.91(Al_0.5Nb_0.5)_0.09O₆陶瓷具有综合最佳的介电性能,ε_r=14.51,Q×f=158120 GHz,τ_f=-13.0 ppm/℃。本文还在上述基础上向Li₂(Mg_0.92Zn_0.08)₃Ti_0.91(Al_0.5Nb_0.5)_0.09O₆介质陶瓷中添加Ba Cu B₂O₅做了降温烧结探索。研究表明,Ba Cu B₂O₅的加入会给体系引入杂相,陶瓷中也会产生液相。虽然烧结温度随Ba Cu B₂O₅的含量增加迅速降低,能够实现降温烧结,但也伴随着品质因子和温度稳定性的下降。降温烧结的陶瓷在1060℃保温4小时可以获得最佳综合性能,ε_r=14.22,Q×f=31054 GHz,τ_f=-15.9 ppm/℃。更多还原

【Abstract】 Wireless communication technology is constantly changing.The joint development of 5G network and a variety of new technologies provides great convenience for people’s current life,which is inseparable from basic material research and application.Various communication related devices made of dielectric ceramics have been widely used in various fields,but also face the challenge of higher requirements in the new era.Therefore,as the basic core material,the research,development and application of new microwave dielectric ceramics have attracted more attention.In this paper,Li₂Mg₃TiO₆ ceramic system was selected as the basic material,and Li₂Mg₃Ti_1-x(Al_0.5Nb_0.5)_xO₆ and Li₂(Mg_1-yZn_y)₃Ti_1-x(Al_0.5Nb_0.5)_xO₆ dielectric ceramics were prepared by doping and replacement at Ti and Mg sites by solid-state method.Then,Li₂(Mg_1-yZn_y)₃Ti_1-x(Al_0.5Nb_0.5)_xO₆+Ba Cu B₂O₅ dielectric ceramics were prepared by cooling sintering with sintering additives.According to the amount of doping,this paper studied the above ceramics from the aspects of ceramic density,phase change,crystal structure,bond valence theory,stacking coefficient and sintering kinetics,and obtained some dependence on the dielectric properties of the ceramics.Li₂Mg₃Ti_1-x(Al_0.5Nb_0.5)_xO₆ dielectric ceramics doped and replaced at the Ti site of Li₂Mg₃TiO₆ by solid-state method are a single phase with rock salt cubic structure in the experimental range.Through the analysis of P-V-L chemical bond valence theory and the calculation of various parameters related to bond properties,it is found that(Al_0.5Nb_0.5)⁴⁺ion doping improved the ionic polarizability,increases the lattice energy,increases the chemical bond valence and decreases the thermal expansion coefficient with the increase of doping amount.These changes work together to improve the dielectric properties of Li₂Mg₃TiO₆ceramics,improved the quality factor,dielectric constant,temperature stability,and reduced sintering temperature.The best dielectric properties are obtained when the doping amount of(Al_0.5Nb_0.5)⁴⁺is x=0.09（ε_r=13.86,Q×f=141210 GHz,τ_f=-25.9 ppm/℃）.On this basis,Zn²⁺ion was further doped and replaced at its Mg site by the same solid-state method.When the doping amount is less than 0.08,the ceramic is a single crystalline phase.Excessive doping leads to the formation of heterophases and worsens the dielectric properties.An appropriate amount of Zn²⁺ion doping can further improve the comprehensive dielectric properties and reduce the sintering temperature.When the doping amount of Zn²⁺ion is y=0.08,Li₂(Mg_0.92Zn_0.08)₃Ti_0.91(Al_0.5Nb_0.5)_0.09O₆ ceramics sintered at 1320℃for 4 hours have the comprehensive optimization dielectric properties,ε_r=14.51,Q×f=158120 GHz,τ_f=-13.0 ppm/℃.Based on this,Ba Cu B₂O₅ was added to Li₂(Mg_0.92Zn_0.08)₃Ti_0.91(Al_0.5Nb_0.5)_0.09O₆dielectric ceramics to explore the cooling sintering.The results show that the addition of Ba Cu B₂O₅will introduce impurity phase into the system,and liquid phase will be produced in the ceramics.Although the sintering temperature decreases rapidly with the increase of Ba Cu B₂O₅ content,ooling sintering can be realized,but also with the decrease of quality factor and temperature stability.The best comprehensive properties can be obtained by holding the temperature at 1060℃for 4 hours,ε_r=14.22,Q×f=31054 GHz,τ_f=-15.9ppm/℃.更多还原