Novel phenomenon on valence unvariation of doping ion in Yb:YAG transparent ceramics using MgO additives

Yb:YAG nanopowders were synthesized by the alcohol-water co-precipitation method adding MgO as sintering additives. Appropriate amount of MgO adding can restrict the agglomeration and reduce the particle size of Yb:YAG powders. When the MgO content was 0.04wt%, well-dispersed Yb:YAG powders with ellipsoidal particles of less than 100 nm diameter were obtained. The experimental results showed the valence variation of doping ion Yb³⁺ would not appear when adding MgO as sintering additives, so ceramics showed colorless transparent instead of green due to Yb²⁺ color center using traditional SiO₂ as additives. The transmission of the sintered Yb:YAG ceramics can reach 80.6% even without annealing. Ceramic morphology showed that the grains had uniform-distribution with the size of 10 μm or so, and no impurity and pore existed in the grain boundary and crystalline while using optimal sintering conditions.     

陈化时间对Nd:YAG纳米粉体制备及性能的影响

以NH4Al(SO4)2·12H2O,Y(NO3)3·5H2O,Nd(NO3)3·5H2O为原料,碳酸氢铵为沉淀剂,研究了共沉淀法制备Nd:YAG纳米粉体过程中陈化时间对粉体性能的影响.采用pH计,FT-IR,XRD和TEM测试手段对其进行表征.陈化过程中PH值先减小后增大,XRD曲线显示共沉淀法中不同陈化时间都能得到纯相粉体,而24h所得粉体最好,粉体TEM图谱表明陈化24h所得到的粉体粒径更小,分散性较其他粉体更好.结果表明:共沉淀法制备Nd:YAG纳米粉体过程中陈化时间不影响纯相粉体的制得,但对粉体粒径大小及分布和团聚程度有直接的影响.陈化24h的粉体颗粒最小并且均匀,团聚很少.     

树立正确观念,提升化学教学质量

文章主要重点从教学理念方面,提出在新教材实施过程中,教师应树立整体育人观,树立新的教育思想,转变育人观念;树立教学服务观,把＂教＂和＂学＂有机统一起来,使教师的＂教＂为学生的＂学＂服务;树立情感教育观,充分发挥情感教学的重要作用,加强师生之间的情感互动;树立目标学习观,依据大纲要求和学生实际,制定合理、具体、确切、科学的课堂教学目标;树立课堂调控观,有效利用课堂教学中的每一分钟,实现课堂教学的最优化;培养创新学习观,培养学生自主探索、自主研究的精神,培养学生的创新能力。