镁固溶对钙钛锆石陶瓷固化体的影响北大核心CSCD

以CaTiO_(3)、ZrO_(2)、TiO_(2)和MgO为原料,经固相烧结法在1350℃下制备镁固溶钙钛锆石陶瓷固化体(Ca_(1-x)Zr_(1+x)Ti_(2-x)Mg_(x)O_(7),0≤x(固溶度)≤0.20),并研究Mg^(2+)固溶度对固化体物相组成、微观形貌和晶体结构的影响。X射线衍射结果表明:Ca_(1-x)Zr_(1+x)Ti_(2-x)Mg_(x)O_(7)结构中的Ti位可容纳固溶度x=0.05~0.15的Mg^(2+);并通过选区电子衍射实验进一步验证,固化体的主要晶体结构为单斜相钙钛锆石(2M,空间群C2/c)。当固溶度x=0.05~0.15时,钙钛锆石产物的相对质量分数高于97%,仅有微量的钙钛矿杂质相生成;随着Mg^(2+)固溶度的进一步增加(x=0.20时),Mg^(2+)浓度超过固溶度极限,使杂质相含量大幅增加。同时,扫描电子显微镜观察结果表明,固化体抛光面结构致密;在Mg^(2+)固溶度x≤0.15时,阳离子浓度符合所设计的化学计量比。

Effects of Solid Solution of Magnesium on Zirconolite Ceramic Wasteforms

Zirconolite ceramic wasteforms with a stoichiometry of Ca_1-xZr_1+xTi_2-xMg_xO₇ (0≤_x≤0.20) were obtained by solid-state sintering of CaTiO₃, ZrO₂, TiO₂, and MgO at 1 350 ℃. The influences of the solid solubility of Mg²⁺ on the phase composition, microstructure, and crystal structure were investigated. The X-ray diffraction results demonstrate that the Ti site in Ca_1-xZr_1+xTi_2-xMg_xO₇ can accommodate Mg²⁺ in a range of x=0.05-0.15, and the main phase of the sample is determined to be a monoclinic-zirconolite structure (2M, space group: C2/c), as further confirmed by the selected area electron diffraction analysis. For the samples of x=0.05-0.15, the relative mass fraction of the zirconolite phase is higher than 97%; only a trace amount of the perovskite impurity can be found. When x increases to 0.20, the concentration of Mg²⁺ exceeds the limit of solid solubility of the structure, resulting in a significant increase in the impurity phase. Meanwhile, the dense morphology of the polished surface is observed by the scanning electron microscope, and the measured cation ratio is in good accordance with the designed stoichiometry when x≤0.15.