Abstract Structural variation in alumina directly determines the thermal stability of transition alumina with La dopant at high temperature. In this work, the thermal stability and alumina structure from well-crystallized ultrafine boehmite doped with various La-bearing compounds were studied. La2O3, LaAlO3, and LaAl11O18 could not efficiently inhibit transition alumina changing into α-Al2O3, α-Al2O3 seed benefited α-Al2O3 formation in the presence of La dopant. La(NO3)3 doping into boehmite effectively improved the thermal stability of θ-Al2O3 above 1200 °C. The nano-diameter active spots with low melting point led to the formation of α-Al2O3 with a smooth edge and sintering neck from the blank boehmite, whereas La dopant contributed to rhombus θ-Al2O3 with considerable pores, jagged edge, and wedge at 1200 °C for 2 h. Moreover, the Al and La contents fluctuated asynchronously during calcination, and the atomic ratio of Al/O decreased with the addition of La dopant. These results are attributed to La migration, assembling in active spots and increasing their melting point. Furthermore, relative to nearly 100% AlO6 coordination in α-Al2O3, La dopant significantly increased the AlO4 content above 900 °C. Therefore, La dopant increased the melting point of the active spots, hindered AlO6 formation, and inhibited α-Al2O3 nucleation on the alumina surface, thereby improved the thermal stability of the transition alumina.

中文翻译：

---

用 La 掺杂剂提高过渡氧化铝热稳定性的结构变化

摘要 氧化铝的结构变化直接决定了掺杂镧的过渡氧化铝在高温下的热稳定性。在这项工作中，研究了掺杂各种含 La 化合物的结晶良好的超细勃姆石的热稳定性和氧化铝结构。La2O3、LaAlO3 和 LaAl11O18 不能有效抑制过渡氧化铝转变为 α-Al2O3，α-Al2O3 晶种在 La 掺杂剂存在下有利于 α-Al2O3 的形成。La(NO3)3 掺杂到勃姆石中有效地提高了 θ-Al2O3 在 1200 °C 以上的热稳定性。具有低熔点的纳米直径活性点导致空白勃姆石形成边缘光滑和烧结颈的α-Al2O3，而La掺杂剂导致菱形θ-Al2O3 具有相当大的孔隙、锯齿状边缘和1200 的楔形℃ 2 小时。而且，煅烧过程中Al和La含量不同步波动，Al/O原子比随着La掺杂剂的加入而降低。这些结果归因于 La 迁移、聚集在活性点中并提高它们的熔点。此外，相对于 α-Al2O3 中接近 100% 的 AlO6 配位，La 掺杂剂在 900°C 以上显着增加了 AlO4 含量。因此，La掺杂剂提高了活性点的熔点，阻碍了AlO6的形成，抑制了氧化铝表面的α-Al2O3形核，从而提高了过渡氧化铝的热稳定性。相对于 α-Al2O3 中接近 100% 的 AlO6 配位，La 掺杂剂在 900 °C 以上显着增加了 AlO4 含量。因此，La掺杂剂提高了活性点的熔点，阻碍了AlO6的形成，抑制了氧化铝表面的α-Al2O3形核，从而提高了过渡氧化铝的热稳定性。相对于 α-Al2O3 中接近 100% 的 AlO6 配位，La 掺杂剂在 900 °C 以上显着增加了 AlO4 含量。因此，La掺杂剂提高了活性点的熔点，阻碍了AlO6的形成，抑制了氧化铝表面的α-Al2O3形核，从而提高了过渡氧化铝的热稳定性。