ZnO超微粉的溶胶-凝胶法制备及晶体生长特征

PREPARATION AND CRYSTAL GROWTH CHARACTERISTICS OF DOPED AND UNDOPED ZnO ULTRA-FINE POWDERS BY SOL-GEL METHOD

利用溶胶 -凝胶法以醋酸锌及硝酸铋和醋酸锰制备了纯ZnO以及Bi2 O3 ,MnO掺杂的ZnO超微粉体 .通过X射线衍射分析和透射电镜分析 ,研究了不同温度和不同掺杂条件下ZnO粉体的生长特征 .结果表明 ,ZnO晶体的生长受掺杂元素和制备温度的显著影响 .未掺杂的纯ZnO晶体生长具有各向同性特征 ,晶体呈各边近相等的六边形 .Bi2 O3 ,MnO掺杂后 ,ZnO晶体表现出显著的定向生长特征 ,晶体呈板状、棒状等形态 .掺杂量为 0 .5 %～ 1.0 %摩尔分数时 ,晶体定向生长最为显著 .70 0℃下制备的Bi2 O3 ,MnO掺杂的ZnO晶体短轴一般为 40～ 180nm ,长轴 2 0 0～ 6 0 0nm ,极少数晶体长径达 2 μm以上 .而进一步提高掺杂量时 ,晶体定向生长则逐渐减弱 .70 0℃下制备的掺杂量为 2 .0 %摩尔分数的ZnO晶体基本上无定向性 .表明ZnO晶体的生长受次晶相的显著影响 .

ZnO ultra_fine powders undoped and doped with Bi 2O 3 and MnO were synthesized by sol-gel method from the sols containing zinc acetate only and its mixture with bismuth nitrate and manganese acetate. The growth characteristics of the crystals doped with different quantities of additives at different temperatures were investigated. XRD and TEM studies show that the growth of ZnO crystals is affected strongly by the temperature and dopants. The growth of undoped ZnO crystals shows isotropic characteristics and its morphology is hexagonal. The ZnO crystals doped with Bi 2O 3 and MnO show preferred orientation growth, with the plank_like and stick_like forms. Highly orientated crystals appear at the contents of 0.5% to 1.0%(in mole) (Bi 2O 3, MnO), and the particles can be obtained at 700 ℃ with the minor axis of 40 to 180 nm and the long axis of 200 to 600 nm, or even longer than 2 μm. But at a higher content of the dopants, the crystal orientation growth gradually disappear. The ZnO crystals doped with 2.0% (Bi 2O 3, MnO) at 700 ℃ did not show any preferred orientation growth. These results indicate that the growth of ZnO crystals is strongly affected by the segregation of the secondary phases.