基于结晶法的YAG粉末制备及其烧结特性

发布时间：2018-05-17 03:30

本文选题：YAG + 粉末　；参考：《华中科技大学》2015年硕士论文

【摘要】：钇铝石榴石(Y3Al5O12,YAG)是一种重要的激光基质材料。相对于YAG单晶,YAG透明陶瓷因其高稳定性、低制造成本和易大浓度掺杂等特点引起了国内外学者的浓厚兴趣,近年来在许多场合已经取代了YAG单晶得到实际应用。高透明YAG陶瓷是制备高质量YAG激光陶瓷的前提。而YAG粉末的烧结特性是影响YAG陶瓷透光率的重要因素之一。因而本论文主要研究目的是探究出一种简单高效、适合工业化生产的YAG粉末合成方法。利用此方法可以在较低温度下合成成分均匀、分散良好、大小适宜的YAG粉末,从而为制备YAG透明陶瓷打下良好的基础。本文首先以硝酸盐体系为原材料采用结晶法来合成YAG粉末,具体研究内容分为三部分:(1)硝酸盐过程。仅仅以Y(NO3)3和Al(NO3)3为原材料,利用二者在水中的大溶解度,通过加热搅拌它们的水溶液,制得Y(NO3)3和Al(NO3)3混合较均匀的结晶前驱体。此结晶前驱体经950oC煅烧后,合成了纯相YAG粉末。制得的YAG粉末经1550oC烧结后,样品中晶粒组成了许多“晶粒团”,“晶粒团”内部晶粒排列整齐,气孔含量很少,而“晶粒团”之间却留有非常大的气孔。(2)Y2O3过程。在硝酸盐过程基础上,在原材料中加入2 wt.%Y2O3纳米粉体,结晶前驱体经过850oC煅烧制备出了纯相YAG粉末,此过程制备的粉末与硝酸盐过程制备的粉末具有相似的团聚性和烧结特性。(3)Y-PAA过程。在Y2O3过程基础上,在原材料中加入占固体材料50 wt.%的聚丙烯酸(Polyacrylic acid,[C3H4O2]n,PAA),经过700oC煅烧合成了分散较好的、纯相的YAG粉末。此过程合成的粉末经1550oC烧结后无“晶粒团”出现,但是晶粒排列不致密。为了进一步改善粉体的烧结特性,接着利用硫酸盐+硝酸盐体系为原材料采用结晶方法来合成YAG粉末。此过程中以相对廉价的Y(NO3)3、Al(NO3)3和Al2(SO4)3为原材料,通过蒸发其水溶液的溶剂,使混合溶液中的离子发生重组而结晶析出饱和盐,按照盐的不同结晶析出顺序构成了三层核壳结构的结晶前驱体,并通过煅烧此结晶前驱体来合成YAG粉末。实验过程中发现,增加原材料中SO2-4的含量,有利于改善粉末分散性,但不利于获得纯相的YAG粉末。当原材料中n(SO2-4)/n(Y3+)=1.5时,煅烧1050oC合成的粉末分散性较优。此粉末经1550oC烧结后平均晶粒尺寸约为1.02um,晶粒分布均匀,表现出最佳的烧结特性。综合分析以上几种方法制备的YAG粉末的颗粒大小、分散性,及其烧结特性,总结出对粉末烧结特性影响较大的因素分别为:(1)分散性。只有高分散的粉末才能在烧结时发生同步生长,从而使得晶粒大小分布均匀,晶粒间气孔含量较少。(2)颗粒大小。粉末一次颗粒越小,粉末的烧结活性越高;但粉末一次颗粒太小,又将会使得烧结中晶粒发生异常长大,使得晶粒分布不均匀。
[Abstract]:Yttrium aluminum garnet (Y _ 3AL _ 5o _ 12) is an important laser matrix material. Compared with YAG crystal transparent ceramics, because of its high stability, low manufacturing cost and easy to doped with large concentration, it has attracted great interest of scholars at home and abroad. In recent years, YAG single crystals have been replaced by YAG in many applications. High transparent YAG ceramics are the prerequisite for the preparation of high quality YAG laser ceramics. The sintering characteristic of YAG powder is one of the important factors affecting the transmittance of YAG ceramics. Therefore, the main purpose of this paper is to explore a simple and efficient synthesis method of YAG powder suitable for industrial production. The method can be used to synthesize YAG powders with uniform composition, good dispersion and appropriate size at low temperature, thus laying a good foundation for the preparation of YAG transparent ceramics. In this paper, YAG powder was synthesized by crystallization method using nitrate system as raw material. The specific research contents are divided into three parts: 1) nitrate process. Using only Y(NO3)3 and Al(NO3)3 as raw materials, using their high solubility in water and stirring their aqueous solution by heating, a more homogeneous crystal precursor of Y(NO3)3 and Al(NO3)3 was prepared. After calcined with 950oC, the pure phase YAG powder was synthesized. After the YAG powder was sintered by 1550oC, many "grain clusters" were formed in the samples. The grains in the "grain clusters" were arranged neatly and the porosity content was very small, but there was a very large process of porosity. On the basis of nitrate process, the pure phase YAG powder was prepared by 850oC calcination of the crystal precursor by adding 2 wt.%Y2O3 nano-powder into the raw material. The powders prepared by this process have similar agglomeration and sintering properties to those prepared by nitrate process. On the basis of Y2O3 process, polyacrylic acidate (50 wt.%) was added into the raw material, [C3H4O2] nacidic acid, [C3H4O2] PAA, was calcined by 700oC to synthesize well dispersed and pure phase YAG powder. The powder synthesized by this process did not appear "grain agglomeration" after 1550oC sintering, but the grain arrangement was not compact. In order to further improve the sintering properties of the powder, YAG powder was synthesized by crystallization method using sulfate nitrate system as raw material. In this process, the relatively cheap Yanno _ 3N _ 3O _ 3AlN _ 3N _ 3O _ 3 and Al2(SO4)3 were used as raw materials to crystallize and precipitate saturated salts by evaporating their aqueous solution solvent and recombination of the ions in the mixed solution. The crystal precursor with three layers of core-shell structure was formed according to the different crystallization precipitation order of salt, and the YAG powder was synthesized by calcining the crystal precursor. It was found in the experiment that increasing the content of SO2-4 in raw materials was beneficial to improve the dispersibility of the powder, but was not conducive to obtaining pure phase YAG powder. When n(SO2-4)/n(Y3 = 1.5 in raw materials, the dispersion of powders synthesized by calcination of 1050oC is better. The average grain size of the powder sintered by 1550oC is about 1.02um, and the grain distribution is uniform, showing the best sintering characteristics. The particle size, dispersity and sintering properties of YAG powders prepared by the above methods are analyzed. The factors that have a great influence on the sintering properties of YAG powders are concluded as follows: 1) dispersity. Only the highly dispersed powder can grow synchronously during sintering, so that the grain size distribution is uniform and the porosity content between grains is less. The smaller the primary particle is, the higher the sintering activity of the powder is, but the smaller the primary particle is, the more abnormal the grain growth will be and the uneven distribution of the grain will occur.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.65

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