【作者】 李远亮；

【导师】 曲远方；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 本文以具有钙钛矿结构的BaTiO₃基陶瓷作为研究对象,分别研究了Sm₂O₃掺杂对（BaxSr1-x）TiO₃、Ba(Sn_xTi_1-x)O₃和Ba（ZrxTi1-x）O₃陶瓷微观结构与介电性能的影响,以及Y₂O₃和NiO掺杂对（Ba_xSr1-x）TiO₃陶瓷微观结构与介电性能的影响。通过对试样微观结构和介电特性的研究,揭示了Sm₂O₃、Y₂O₃和NiO在BaTiO₃基陶瓷中的掺杂机理。研究结果发现:Sm₂O₃和Y₂O₃在(Ba_xSr_1-x)TiO₃陶瓷中,随着掺杂量的增加,Sm³⁺和Y³⁺有一个优先取代位置,也就是在它们掺杂的起始阶段,Sm³⁺和Y³⁺主要进入晶格A位位置,而在其掺杂量超过某个量之后,则以进入晶格B位位置为主,这种优先取代结果导致试样晶胞参数a随掺杂量的增加先减小后增大,试样介电常数先增大后减小。两者都能使试样介电损耗得到改善,尤其是当Y³⁺掺杂量为1.0 mol%时,试样介电损耗降低到0.0015。两者掺杂结果的显著不同在于Y³⁺掺杂使试样表现出了弥散相变特性,而Sm³⁺掺杂却没有。当NiO被添加到（BaxSr1-x）TiO₃陶瓷中时,只有一少部分Ni²⁺离子进入晶格的B位取代Ti4+离子,导致试样晶格参数轻微增加,之后NiO主要在晶界附近聚集,形成BST/NiO复合材料。试样介电常数随NiO掺杂量的增加而下降,介电温谱显示含Ni试样具有弥散相变特性,且随掺杂量的增加,效果越明显,这也使试样介电温谱得到了很大改善。Sm₂O₃的加入并不改变BTS10和BZT20陶瓷的主晶相结构,与空白试样相比,掺杂微量Sm³⁺会使晶粒尺寸下降。随着Sm₂O₃掺杂量的增加,BTS10和BZT20陶瓷试样介电常数先增大后减小,当试样介电常数最大时,其介电损耗也最高。BTS10和BZT20陶瓷试样Tm和Sm₂O₃掺杂量之间的变化规律大致相似,不同点在于BTS10陶瓷的Tm在Sm₂O₃掺杂起始阶段并不改变。掺杂Sm₂O₃的BTS10和BZT20陶瓷试样均具有弥散相变特性,但二者有两点明显不同,其一,BTS10空白试样本身并不具有弥散相变特性,而BZT20空白试样即具有弥散相变特性。其二,随Sm₂O₃掺杂量的增加,BTS10陶瓷试样弥散特性一致增强,而BZT20陶瓷试样弥散特性却是先变弱后增强。这种差别说明,在Sm₂O₃掺杂起始阶段,一部分Sm³⁺进入了BTS10陶瓷晶格B位位置,而在BZT20陶瓷中却没有,而两者试样Tm在Sm₂O₃掺杂起始阶段变化的差异性也说明了这一点。更多还原

【Abstract】 The effects of Sm₂O₃, Y₂O₃ and NiO on microstructure and dielectric properties in BaTiO₃-based ceramics are investigated, respectively. Based on the effects of Sm³⁺, Y³⁺, and Ni²⁺ on the microstructure and dielectric properties, the substitution mechanism of Sm³⁺, Y³⁺, and Ni²⁺ in BaTiO₃-based ceramics is also investigated and discussed, respectively. The research achievements are as follows:There is an alternation of substitution preference of Sm³⁺ and Y³⁺ for the host cations in perovskite lattice, that is, Sm³⁺ and Y³⁺ enter the A site in perovskite lattice at first, then they enter the B site when the additive amount of Sm³⁺ and Y³⁺ exceed some value. Owing to the substitution preference, the crystal cell a and dielectric constant rise at first, if the amount continues increasing, they will decrease. Both Sm³⁺ and Y³⁺ can improve the dissipation factor, especially, the optimized dissipation factor is 0.0015 for 1.0 mol%-Y³⁺-doped samples, making it a superior candidate material for applications. There is an obvious distinction for the effects on dielectric properties between Sm³⁺ and Y³⁺, that is, the Y³⁺, not Sm³⁺, makes the BST ceramics exhibit the diffuse phase transition.It is also found that Ni²⁺ can enter the B site in ABO₃ perovskite at first, making the crystal cell a rise, whereafter, Ni²⁺ ions most segregate on the grain boundaries to inhabit the grain growth, forming the BST/NiO composites. Due to the decrease of grain size and the impurity, the dielectric constants are decreased. It is concluded that the diffuse phase transition is linked to the adulteration of Ni²⁺, and the diffuse phase transition increases with the doping level increasing, leading to that the peaks of dielectric constants become slower and flatter.The results indicate that the crystal structures are perovskite phase for all of the examined samples in BTS10 and BZT20 ceramics, however, contrasting to the blank sample, the grain size of the sample with Sm₂O₃ addition is decreased. Owing to the substitution of Sm³⁺, the dielectric constant rises at first, if the amount continues increasing, it will decrease, in the mean time, the dissipation factor also comes to its maximum when the dielectric constant is the highest. The relation between Tm and the concentration of Sm₂O₃ has some similarity except that Tm does not move in BTS10 ceramics at first, resulting from a handful of Sm³⁺ entering into the B site. All of the samples exhibit the diffuse phase transition with Sm₂O₃ addition, however, there are two obvious distinction among BTS10 and BZT20 ceramics. First, the blank sample of BTS10 has no diffuse phase transition in nature, the samples of BTS10 can exhibit diffuse phase transition only when the Sm³⁺ ions are added, on the contrary, the blank sample of BZT20 possesses the diffuse phase transition in nature. Second, the diffuse phase transition congruously increases with the level of the Sm³⁺ doping increasing in BTS10 ceramics, however, the diffuse phase transition lowers in the beginning in BZT20 ceramics, if the amount continues increasing, it will increase, which demonstrated that a handful of Sm³⁺ ions have entered into the B site in BTS10 ceramics but not in BZT20 ceramics in the beginning, proved by the distinction of the relation between Tm and the concentration of Sm₂O₃ at first.更多还原