Synthesis of Yttrium Oxide Nanocrystal via Solvothermal Process

JOURNAL OF RARE EARTHSVol.24 , Spec. Issue , Dec.2006 ,p. 47Synthesis of Y trium Oxide Nanocrystal via Solvothermal Process'Guo Huang(郭煌) , Hong Zhanglian(洪樟连)* , Zhang Shizhu(张世著)' , Zhang Pengyue (张朋越)'2 ,Fan Xianping(樊先平)'( I. Department of Materials Science and Engineering ，Zhejiang University ，Hangzhou 310027，China ;2. Magnetism Key Laboratory of Zhejiang Province , China Jiliang University , Hangzhou 310018 , China )Abstract : Y2O3 nanomaterials have been widely used in transparent ceramics and luminescent devices. Recently there aremany studies focusing on contolling the size and morphology of Y2O3 in order to obtain better materials performance. In presentstudy , ytriurm oxyhydroxide precursor was synthesized via a facile solvothermal process through the disoltion-recrytallizationmechanism of Y2O3 raw powders in the ethylenediamine solvent , then nanosized ytrium oxide crystal was prepared from the pre-cursor through post heat treatment process. The effects of solvothermal treatment temperature , holding time , solvent kinds andpost heat treatment parameters on crystalline structure , grain shape and size of nanocrystal were investigated by XRD ,TEMand TGA-DTA measurements. TEM images reveal that the morphology of product after post heat treatment at 460 C for 12h is rice-like nanocrystal. XRD shows that this product is pure cubic Y 203 cphase. Present study reveals that high purityY203 with rice-like morphology can be easily prepared with average size around 30 nm under suitable post heat treatmentparameters. In addition , the effects of solvents such as water and ethanol etc. on the crystal structure and morphology werealso investigated. It is suggested that dissolution- recrystallization process may be the main mechanism for the formation ofnano-sized YOOH precursors under solvothermal reaction condition , and the ethylenediamine solvent is likely to play animportant role in controlling the transformation process of yttria precursors to theY2O3 nanocrystal.Key words : ytrium oxyhydroxide ; ytrium oxide ; nanocrystal ; solvothermal process ; rare earthsCLC number :TQ174. 75Document code : AArticle ID : 1002 -0721( 2006 )- 0047 -04In recent years , nanocrystals have attracted reproducts of yttrium oxide , calcinations or post heatsearchers interest because of their unusual behav-treatment procedures are necessary and the heat treat-iors27. Rare earth related nanocrystals3I , espe-ment temperature is usually as high as 800 C. There-cially the nanosized yttrium oxide( Y203 ) with control-fore , the whole procedure to produce nanosized Y2O3lable size and morphology , which may have better sin-crystal is very complicate and , usually is easily suf-tering ability and unique luminescent property , havefered from the contamination of undesired impuritybeen widely studied because of their potential applica-species in the final products. The impurities may betions in transparent ceramics and luminescent de-harmful for the luminescent performance.vices56] , such as FED and CRT , etc.Therefore , it is still important and necessaryWet chemistry methods ，including sol-gelto develop a simple and efficient fabricationroute' , combustion synthesis procedure' 5 , micro e-process , free of catalyst or template species , tomulsions methodf 9] , hydrothermaland solvother-obtain the final nanosized Y2O3 crystal in currentmal 121 methods etc. , were applied to prepare nano-research activities. In this paper , a facile solvocrystals including the Y2O3 nanocrystal which wasthermal process free of any catalyst or template hasstudied in present study. However , wet chemistrybeen developed for the preparation of nano-Y 00Hmethods usually adopt catalyst or template to obtainprecursor. The nano- YOOH precursor , which hasvarious precursors for ytrium oxide. In general , thehigh purity and better transformation ability to theprecursors include yttrium hydroxide and yttrium car-final nanosized Y2O3 crystal after the post heatbonate，etc. Therefore ，in order to obtain desiredtrea中国煤化Iequently used as pre-CNMH GReceived date :2006 -06 -25 ; revised date :2006 -09 -08Foundation item : Project supported by SRF for ROCS , SEM ( 2003-14 ) and Science and Technology Department of Zhejiang Province( 2003C1 1027 )Biography Luw Huang( 1981 - ) , Male , Master candidateCorrespondanguthor ( E-mail : hong_ zhanglian@ zju. edu. cn)48JOURNAL OF RARE EARTHS , Vol. 24 , Spec. Issue , Dec.2006cursor to prepare nanosized Y2O3 crystal. In addi-Fig. 1 shows the XRD patterns of the as-preparedtion , suitable synthesizing conditions to synthesizeyttria precipitate and the precursors prepared via sol-the YO0H and Y2 03 nanoerystal were suggested invothermal process under different reaction tempera-present reaction system.tures for 12 h. Before the solvothermal treatment , the1 Experimentalcorresponding XRD pattern ( 1 ) shows a bumpedIn a typical synthesis condition , 5 mmol Y203background , which reveals the presence of large apowder( purity : 99.999% ) was dissolved in 3 mlmount of amorphous phase , and the diffraction peaksconcentrated nitric acid ( analytical purity ) to prepareare consist with that of a monoclinic lattice of Y( OH );Y( NO3 ), solution. Followed by the dropwise addition( JCPDS No. 21-1447 ).of the4 mol. L-' KOH solution used as the precipi-After solvothermal reaction above 250 C fortant , the pH value of the mixture solution was adjusted12 h ,all difaction peaks of pattern( 2 ) and( 3 ) can .to be about 11. After aging completely , yttriurm gelsbe well indexed to the monoclinic phase of YOOHwas fitrated and washed with distilled water for several( JCPDS No. 20-1413 ) ,and no other phase can be de-times ,and then dried at 110 C in a vacuum oven.tected. However , when the solvothermal reaction wasThen , the as-prepared precipitate was moved into aconducted at 300 C for 12 h or long time , a weakquartz tube and then placed into a 250 ml capacitypeak in the Fig. 1 ( d ) appears. Based on the phasestainless steel autoclave ，which was subsequentlydiagram of Y2O3-H2O system". , such situation mayfilled with ethylenediamine ( analytical purity ) up tooccur when the transformation from YOOH to Y2O385% of the total volume. The autoclave was heated ,( JCPDS No. 44-0399 ) starts. It is dificult to deter-and maintained at 250 ~300 C for 3 to 12 h. Thenmine the new phase formed at 300 9C just from thisthe autoclave was cooled to room temperature. The asweak peak with diffraction angle of about 28 degree.prepared precursor was collected and washed with theIn addition , the influence of reaction time from 3distilled water and ethanol , and then dried at 80 C.to 12 h at 300 C was investigated too. The XRD pat-During the post heat treatment process , the dried pre-terns were essentially identical which could be attribu-cursor was heated at 460 C for2 h in furmace , finallyted to the YOOH phase. With increasing reactionthe obtained product was collcted for further measure-time，the peaks became sharp and strong , implyingments.that particle growth takes place and the crystal struc-The crystal strueture and phase of products weredetermined by X-ray diffraction ( XRD ). The XRDture grows perfectly with increasing reaction time.The morphology and grain size of the precursorpatterns were recorded with a standard diffractometer( Rigaku MAX-RD , Japan ) equipped with a graphitewere investigated by TEM observation. As shown inmonochromator using Cu Ka radation( λ = 0.15405Fig. 2 , the YOOH phase formed during solvothermalreaction is nanocrystal with well shape. The morphol-nm ) operating at 40 mA and 40 kV. A scanning rateof4(°) min~' was employed in the 20θ range from▲YOOH10° to 80°. The size and morphology of the products口Y(OH),were examined by transmission electron microscopy( TEM ,JEOL 200CX ) , using an accelerating voltageof 200 kV. TGA-DTA data was recorded with Thermalu swJhnwMmm (3)Analysis Instrument ( SDT Q600 , TA Instruments.New Castle , DE ) with the heating rate of 10 C .(2nin~' under air atmosphere.2 Result and Discussion2. 1 Solvothermal treatment of as-prepared yt-0304050607080tria precipitate中国煤化工Under the solvothermal reaction condition , theMHC N M H Gpared peipitate( 1) andas-prepared ytria precipitate tends to dehydrate andthe precursors prepared via solvothermal process underre-crystallize. The reaction temperature , holding timetemperatures of 250 C(2),280 C(3 ) and 300 C .and solvent kinds may influence the phase transforma-(4 )for 12 htion process , the final phase composition , particle sizeand morphology of the as-hydrothermaled precursors.Guo H et al. Synthesis of Yttrium Oxide Nanocrystal via Solvothermal Process49(ab)reaction temperature in present solvothermal systemfree of catalyst and template.2.2 Post heat treatment of yttria precursorThe TG-DTA measurements were carried out todetermine thermal behavior and decomposition reaction0.2 umof the YOOH precursor. As shown in Fig.3 ,a large(camount of weight loss in the TGA curve was found inthe temperature range of 370 ~460 C , and the weightloss is about 10% which is in agreement with the theo-人retical weight loss for the YOOH -→Y2O3 transforma-tion ,plus the weight loss of dehydration of absorbed0.2 μmwater. A corresponding endothermic peak in the DTAcurve was observed around 440 C. This temperatureFig.2 TEM images of the as-prepared precipitate( a ) and theis lower than that required for decomposition of yttriumproducts prepared via solvothermal process at 300 Chydroxide and yttrium carbonate , which was reportedfor different times of3 h(b),6h( c )and 12 h( d)at 700 ~800 C for classical micro powder 711ogy of YOOH phase , which has small grain size of a-Based on above TG-DTA measurements ，thebout several dozens nanometers , is different from thatYOOH precursor obtained via solvothermal reaction atof the as - prepared precipitate. Furthermore , the300Cfor3hwascalcinedat460Cfor2htopre-grain size becomes large with increasing reactionpare Y203 powders. XRD analysis( Fig. 4 ) shows thattime. Thus , dissolution-ecrystallization process 1the nanosized YOOH phase has transformed completelycould be applied to explain the growth process ofto cubic Y20鸿phase ( JCPDS No. 41-1105 ) withoutnanosized YOOH precursor. Firstly ，the as-pre-any other impurity phase after heat treatment at 460 Cpared precipitate was amorphous and containedpoorly crystallized Y( 0H ); precipitate phase( seeFig. 1( 1 )). When the solvothermal reaction goes9-- Ton , Y( 0H ); was likely to dehydrate and dissolveinto the solvent , then the Y 00H phase re-crystal-lized from supersaturated solution. With the increas-1438.80Cing reaction time , the crystallite degree of YOOH8DTG-was improved ，and the corresponding grain withrice-like morphology and good dispersion grew to0 200 400 600 800 1000 120030 ,50 and 100 nm when the reaction time increa-Temperature/CFig.3 TG-DTA curve of products prepared via solvothermalses from 3 ,6 and 12 h , respectively.reaction at 300 C for3 hIn general , the grain growth based on the dis-solution-recrystallization mechanism is sensitive tothe reaction temperature and pressure of reactionsystem in which the solvent plays an important role. .In order to investigate the influence of various sol-(1)vents on the formation of YOOH phase , ethanol andwater were replaced for ethylenediamine while otherconditions kept unchanged. The XRD resultsshowed that the major product w as amorphous which2)|contained small fraction of poorly crystallized YOOH中国煤化工60~ 70 80phase. Therefore , it was suggested that , in eitherYHCNM HGwater or ethanol solvents , only initial transformationFig.4 XRD patterns of the product calcined at 460 C for2 hfrom Y( 0H ); to Y00H occurred.Above results( 1 )and JCPDS card 41-1105 of cubic Y,0,(2)clearly indicated that ethylenediamine may promote thetransformato市執据Y( OH ), to YOOH at relative lo5(JOURNAL OF RARE EARTHS , Vol. 24 , Spec. Issue , Dec. 2006[2] SiR ,Zhang Y W , YouLP ,et al. Rare-earth oxidenanopolyhedra , nanoplates and nanodisks[ J ] Ange-wandte Chemie-International Edition , 2005 ,44( 21 ):3256.[3] XuG , Zhang Y W ,Liao CS,et al. Tetragonal-to-茶monoclinic phase transitions in nanocrystalline rare-earth-stabilized zirconia prepared by a mild hydrothermal meth-od[J] J. Amer. Ceram. Soc. ,2004 ,87( 12 ):2275.[4] WangX ,SunX M,YuDP ,et al. Rare earth com-100 nmpound nanotubes[ J ] Adv. Mater , 2003 , 15( 17 ):1442.[5] Ronda C R ,Justel T , Nikol H. Rare earth phosphors :Fig.5 TEM image of nano-sized Y2O3 product calcined at 460fundamentals and applications [ J ] J. Alloys Comp.C for2h1998 ,275 -277 :669.[6] lkegami T ,LiJG ,Moti T ,et al. Fabrication of trans-for2 h. And TEM observation of the as-prepared cu-parent yttria ceramics by the low-temperature synthesis ofbic Y2O3 phase ( Fig. 5 ) shows that the correspondingytrium hydroxide[ J] J. Am. Ceram. Soc. ,2002 ,85 :particle maintains its precursor' s rice-like morphology1725.and the average grain size is about 30 nm , slightly[7] Dupont A ,Parent C , Garree B L. Size and morphologysmaller than that of the precursor.control of Y203 nanopowders via a sol-gel route[J] J3 ConclusionSolid Chem. ,2003 , 172 :152.In summary , YOOH nanocrystal was synthesized[8] Tao Y ,Zhao G ,Zhang W ,et al. Combustion synthesisand photoluminescence of nanocrstalline Y2O3 : Euvia a facile solvothermal process , the effects of solvo-phosphors[J] Mater Res. Bull. ,1997 ,32( 5 ):501.thermal temperature , holding time and solvent kinds[9] Hirai T ,Hirano T ,Komasawal. Preparation of Y2O;:on the crystallite structure , grain size and morphologyEu'* phosphor fine particles using an emulsion liquidwere investigated. The ethylenediamine solvent wasmembrane system[ J ] J. Mater. Chem. , 2000, 10found to promote phase transformation from Y( OH ),( 10 ):2306. .to YOOH at lower reaction temperatures in present sol-i 10] TangQ ,LiuZG ,LiS ,et al. Synthesis of ytrum hyvothermal system. It was found that the YOOH precur-droxide and oxide nanotubes[ J ] J. Crystal Growth ,sors prepared by solvothermal process have high purity2003 ,259 :208.and better post heat-treatment ability than classical yt-[11] Li QS,FengC H ,JiaoQ Z ,et al. Shape controlledtria precursors , the nano-sized Y2O3 crystalline couldsynthesis of yttria nanocrystals under hydrothermal condi-be easily obtained from the YOOH precursors aftertions[J] Plhys. Stal. 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