Zr^(4+)对固相反应制备堇青石材料晶相转变的影响

Influence of Zr^(4+) on Phasetransition of Cordierite Material Prepared by Solid Reaction

以菱镁矿风化石、工业氧化铝和二氧化硅微粉为原料,加入不同含量二氧化锆添加剂,通过固相反应合成制备堇青石。用XRD法和SEM法表征试样中的晶相和显微结构,用X′Pert Plus软件对结晶相的晶胞参数和结晶度进行分析,用半定量法对试样晶相组成进行计算,用Scherrer公式计算堇青石的晶粒大小。研究分析Zr4+对制备堇青石材料中晶相组成、晶粒大小、晶胞常数、结晶度及显微结构的影响。结果表明:Zr4+对堇青石结构中Mg2+的置换固溶作用使堇青石相晶胞常数及晶胞体积发生变化,形成的结构缺陷使堇青石结构中离子扩散速度加快。由于Zr4+较高的电场强度,减弱了Mg-O的键力,氧化铝和二氧化硅通过固相反应形成莫来石相。当二氧化锆加入量为1.2%时,堇青石晶胞常数和晶胞体积最大,堇青石晶粒最大,堇青石结构中莫来石含量达到2.5%。

Cordierite was prepared by solid reaction of raw materials including decomposed magnesite, industrial alumina and SiO2 powder with different content of zirconia as additive. Crystalline phases and microstructure were determined by XRD and SEM respectively. The lattice parameters and crystallinity of the crystalline phases were estimated by X＇ Pert plus software. The phase composition was evaluated by Semi-quantification method, and grain size was calculated by Scherrer formula. The effect of Zr4＋ on composition, grain size, lattice parameters, crystallinity and microstructure of crystalline phases was studied. Results show that the lattice parameters and lattice volume of cordierite were affected by the substitution of Zr4~ for Mg2~ in the structure of cordierite. Structure defects caused by Zr4~ could accelerate diffusion of ion in the structure of cordierite. The band of Mg-O is weakened by the interaction of Zr4＋ with higher intensity of ionic field, which results in mullite due to the interdiffusion and solid reaction of A1203 and SiO2. Adding 1.2% zironia, the lattice parameters, lattice volume of cordierite and grain size of cordiertie reached maximum, and 2.5% mullite in the cordierite was observed.