TeO_2薄膜非水解溶胶-凝胶法制备及聚合机制

Preparation of TeO_2Thin Film by Nonhydrolytic Sol-gel Method and Its Polymerization Mechanism

分别以1,2-丙二醇碲和四氯化碲为原料,采用非水解溶胶-凝胶法制备TeO2薄膜.研究了非水解溶胶-凝胶聚合过程的聚合机制以及TeO2薄膜热处理过程中的微观结构变化.研究结果表明,1,2-丙二醇碲为链状齐聚团簇结构,齐聚团簇间通过非水解脱醚聚合反应形成凝胶网络;四氯化碲则先与乙醇发生部分取代反应生成中间产物氯代乙醇碲,中间产物间发生非水解脱氯代烷聚合反应形成凝胶.分析表明,2种凝胶中残余有机基团的数量和所处地位存在差异,其造成薄膜中的Te4+以不同方式还原为Te0.脱氯代烷聚合凝胶网络中残余的氯离子会造成薄膜中非桥氧数目增加,并导致Te2O5晶体析出.随着煅烧温度提高,金属Te和Te2O5分别氧化分解为TeO2,同时依次析出了β-TeO2和-αTeO2.

TeO2 thin films were prepared by nonhydrolytic sol-gel method with tellurium 1,2-propylene diglycollate and tellurium tetrachloride as raw materials,respectively.The nonhydrolytic sol-gel polymerization mechanism and the microstructure transformation process of the gel films during calcining were studied.The results show that tellurium 1,2-propylene diglycollate can form chainlike polymeric molecules,and the nonhydrolytic condensation reaction proceeds between the associated molecular clusters through ether elimination.When tellurium tetrachloride was used as raw materials,the intermediate products tellurium chloride ethoxide were firstly generated by the partly substitution reaction of TeCl4 and C2H5OH.And then the nonhydrolytic condensation reaction took place between these intermediate products via alkyl chloride elimination.The results show that metallic Te formed by different way in the gel films during the films are annealed,which is relative to the amount and position of residual organic component in the gel thin films.When the gel thin films prepared through alkyl chloride elimination nonhydrolytic sol-gel process,there are more non-bridging oxygen and the crystal of Te2O5 in the films,which is attributing to the residual chloride ion in the network structure of gel thin films.With the increasing of annealing temperature,metallic Te and Te2O5 were re-oxidised and decomposed into TeO2,respectively,and the crystal ofβ-TeO2 and α-TeO2 sequentially formed in the thin films.