Efficiently Exfoliated From The Layered Rare-Earth Hydroxides And Their Application In Transparent Ceramic Films

This dissertation focuses on the studies of two kinds of inorganic layered materialsincluding nitrate-type layered rare earth hydroxides(LRHs)and montmorillonite(MMT),which were efficiently delaminated into unilamellar nanosheets via hydrothermal ion exchange,intercalation,inter-layer expansion,and mechanic disturbance.YAG transparant ceramic films were constructed with the nanosheets as building blocks,which is a new technology for transparant ceramics.Detailed characterizations of the products were performed by the combined techniques of XRD,FT-IR,FE-SEM,TEM,SAED,AFM and PLE/PL analysis.The main conclusions are as follows:The hexagonal particles of(Y0.99-xTb0.01Eux)2(OH)5NO3·nH2O(0?x?0.06)and(Y0.99-xGdxCe0.01)2(OH)5NO3·nH2O(0?x?0.5)(LRH)with lateral size of?10 ?m have been hydrothermally synthesized at 180? for 24 h.After hydrothermal ion-exchange at 120? for 24 h,the nitrate ions in LRH interlayer were all replaced by dodecyl sulfonate ions,meanwhile the interlayer was effectively expanded.The free cation(Na+)in the interlayer of natural stratified compound montmorillonite(MMT)was completely replaced by the organic macromolecule(C19H42N+)at 80 ? in water bath,thus yielding an expanded interlayer.Single-layer nanosheets can be easily exfoliated from the the exchanged compounds LRH-DS and MMT-C19H42N+in formamide solution.YAG transparent ceramic films were obtained by spin-coating the colloidal suspension ofexfoliated LRH nanosheets or LRH and MMT nano sheets on sapphire,respectively,followed by calcinations.Increasing the Eu3+ and Gd3+ contents resulted in increased lattice parameters of YAG:Tb3+,Eu3+and(Y,Gd)AG:Ce3+films gradually.It is found that higher calcination temperature is favorable for the orientation growth of the(420)crystal plane.The prepared YAG transparent ceramic films have a high transmittance.Under the excitation of 273 nm,YAG:Tb3+,Eu3+transparent ceramic films exhibited color-tunable emissions,which can be widely tunned from yellowish green to orange by adjusting the Eu3+/Tb3+atomic ratio.(Y,Gd)AG:Ce3+transparent ceramic films exhibit typical yellow emissions centered at 550 nm under the excitation of 450 nm.Red-shifting and enhancedfluorescence intensity were found at a higher Gd3+content.