共沉淀制备ZrO_2(MgO)前驱物的相及晶粒的发育

Evolution of Phase and Grain of Precursor of MgO-ZrO_2 Fabricated by Coprecipitation

MgO 掺杂的 ZrO_2的前驱物用 ZrOCl_2和 MgCl_2的水溶液在 NH_4OH 作用下以共沉淀的形式制备.前驱物可能为 Zr(OH)_4及 Mg(OH)_2与水的络合物.用热重分析、差热分析和 X 光衍射测定研究了前驱物直至1600℃的热分解过程.结果表明热分解所产生的四方相比纯的氢氧化锆分解的有更宽的存在范围.所研究的 MgO 掺杂范围为4.6～8.5mol%.在低 MgO 掺杂水平下,亚稳四方相在较低的温度下就开始向单斜相转变.随着 MgO 掺杂量增加到8.5mol%,亚稳四方相可在高于900℃下存在.研究表明高温形成的四方相可以亚稳到较低的温度.结合热分解产物的透射电子显微镜观察,对 MgO 在四方相亚稳存在中所起的作用进行了讨论.

MgO-doped ZrO_2 precursor was prepared by coprecipitating mixed aqueous solution ofZrOCl_2 and MgCl_2 with NH_4OH.The precursor may be a complex of Zr(OH)_4 and Mg(OH)_2containing water.The thermal decomposition up to 1600℃ of the precursor was investigatedby TG,DTA,and X-ray diffraction.The results showed that the metastable tetragonal phaseof ZrO_2 formed during thermal decomposition can-exist in a wider temperature range thanthat derived from undoped zirconium hydroxide.The metastable tetragonal zirconia begins totransform to the monoclinic one at lower MgO doping concentration.However the metastabletetragonal phase can exist at temperature higher than 900℃ as doping concentration of MgOis increased to 8.5mol%.The role played by MgO in stabilizing tetragonal phase was discussedtogether with TEM observation of powder grains derived from the precursor.