随着多层陶瓷电容器（MLCC）器件的高容量化、轻量化、小型化趋势，市场对钛酸钡（BT）粉体要求更高。钛酸钡粉体的轴率（c/a）、分散性（或称分散度pdi）、粒径、形貌等质量指标对MLCC的烧结性能和介电性能具有重要的影响；水热法合成BT粉体具有纯度高、不需要二次球磨、粒径小等优点，但大多数水热法合成出的BT粉体是立方相和四方相的混合相（c/a值在1.0070~1.0090之间），同时纳米粉体的团聚造成尺寸分布不均匀，这些缺陷制约了水热合成BT粉体的应用发展。因此，本文以Ba(OH)₂•8 H₂O-TiO₂-NH₄OH体系为基础原料，先在两步水热法中探究反应温度、反应时间、钡钛比、钛源种类、二氧化钛尺寸等条件对合成粉体高轴率的影响，比较了其合成颗粒的特征，初步优化出合成高轴率BT粉体的最佳合成条件；再探究并比较单一分散剂聚乙烯基吡络烷酮（PVP）、十六烷基三甲基溴化铵（CTAB），组合分散剂（PVP/CTAB）对BT粉体的分散性、粒径、形貌的影响；最后我们提出了一种改善粉体尺寸、分散性的组合优化机制。其研究结果如下：

1. 在两步水热法中，随着温度从200 ℃升高到240 ℃，时间从12 h增加到36 h，粉体颗粒逐渐由空洞结构转化为实心结构、形貌规整，尺寸增加，轴率（c/a）增加；钡钛比增加有利于竞争成核，导致尺寸减小；钡浓度增加，钡离子扩散增加，钡空位减少，有利于合成四方相BT粉体，c/a增加；以大尺寸锐钛矿相TiO₂为钛源可以获得较高的轴率，小尺寸TiO₂的结晶度较低不利于合成四方相BT；金红石相TiO₂抑制粉体四方相的合成；当以偏钛酸和钛酸四丁酯为钛源时，由于钛源本身含有较多的羟基，不利于脱氢过程，得到的BT粉体轴率小。因此，在两步法中，以大尺寸（191/88 nm）、锐钛矿相、TiO₂为钛源，Ba(OH)₂•8H₂O为钡源，醇水比为1:1，钡钛比为4:1，氨水加入量为142 mL/L，第一步反应温度100 ℃、时间10 h，第二步反应温度240 ℃、时间48 h时可以获得c/a为1.0101的BT粉体，非常接近理想轴率1.011。

2. 在合成出高轴率BT粉体后，对比了单一分散剂PVP、CTAB和组合分散剂（PVP/CTAB）对合成BT粉体的轴率、分散性和尺寸的影响，结果表明：缺乏分散剂的情况下，两步水热法合成的钛酸钡还普遍存在分散性差、尺寸较大等缺点；添加单一分散剂后，粉体的分散性得到很大改善，粒度分布曲线由原来的双峰变为单峰，尺寸减小、轴率降低；加入组合分散剂后，pdi值降低更小，分散性更好，轴率、尺寸进一步降低。

3. 通过红外表征、透射测试分析了粉体表面的官能团、包覆层厚度和元素分布，揭示了组合分散剂的分散机理优势：大分子PVP依靠氢键吸附在粉体表面，小分子CTAB依靠静电吸附力包覆粉体实现分散、抑制生长。大分子由于自身缠绕会阻碍氢键形成效率，分散效果不佳。小分子的简单吸附容易在高温环境下被破坏，对粉体的分散和尺寸的控制效果不理想；当小分子与大分子组合使用时，小分子一方面充当“润滑剂”减少大分子自身缠绕，促进大分子PVP形成更多氢键；另一方面，小分子也能局部包覆粉体起到协同作用加强粉末的尺寸和分散性控制效果。

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