Preparation of Lanthanum Oxide Nanoparticles by Chemical Precipitation Method Qiuli ZHANG a, Zhenjiang JI b, Jun ZHOU c, Xicheng ZHAO, Xinzhe LAN

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1 Materials Science Forum Online: ISSN: , Vol. 724, pp doi: / Trans Tech Publications, Switzerland Preparation of Lanthanum Oxide Nanoparticles by Chemical Precipitation Method Qiuli ZHANG a, Zhenjiang JI b, Jun ZHOU c, Xicheng ZHAO, Xinzhe LAN Xi an University of Architecture and Technology, Research Center of Metallurgical Engineering & Technology of Shaanxi Province, Xi an , China a qiulizhang@126.com, b jizhenjiang@126.com, c xazhoujun@126.com Keywords: Lanthanum oxide, nanoparticles, precipitation method Abstract:This paper investigated synthesis of Lanthanum oxide nanoparticles by precipitation method. Effects of reactant concentration, precipitator and dispersant agent on properties of Lanthanum oxide particles were studied. Lanthanum oxide particles were characterized by XRD and SEM. Experimental results showed that ammonium bicarbonate and PEG20000 were appropriate precipitation and dispersant respectively. The optimum process conditions were as follows: concentration of Lanthanum nitrate was 0.18mol/L, concentration ammonium bicarbonate of was 0.6mol/L, reaction temperature was 30. The average particles size of Lanthanum oxide powders with spherical shape gained was about 188 nm. 1. Introduction Rare earth oxides have wide applications such as catalytic materials, magnetic materials, hydrogen storage, optical glass, optical fiber and luminescent materials and other fields [1-6]. In recent years, Lanthanum oxide nanoparticles have been extensively studied owing to their exceptional luminescence, magnetic and electronic properties, which are significantly different from those of bulk materials. Therefore, a series of methods were proposed for the preparation of nanosized Lanthanum oxide, such as homogeneous precipitation, hydrothermal synthesis and various special pyrolysis or decomposition methods [7-9]. Among them, the precipitation technique demonstrated promising development in fabricating Lanthanum oxide nanoparticles due to advantages of low cost, mild synthesis condition and easy scale-up. In the present work, it was attempted to study the reactant concentration, dispersing agent and temperature on the formation of Lanthanum oxide particles. The particle size, morphology, shape and crystalline structure of resulting particles were also demonstrated and discussed. 2. Experimental Raw materials used were aqueous Lanthanum nitrate, ammonium acid carbonate, ammonium oxalate, ammonia, n-butyl alcohol, polyethylene glycol (molecular weight: 400 and 20000, known as PEG-400 and PEG-20000), polyvinyl pyrrolidone(pvp) and other reagents, all of which were of analytical purity. Doubly distilled water and absolute ethanol were used as solvents. Typically, La(NO 3 ) 3 was dissolved in doubly distilled water. This was followed by the addition of a different amount of additives. Precipitant solution was added drop-wise for 75 min. The mixture was left to stir continuously for 0.5h for the reaction to complete. The precipitates were washed several times with doubly distilled water and ethanol alternatively, then were placed in the oven and heated at 80 for 5h. Subsequently, dried powders were calcined at 800. A final superfine powder was obtained. Powder morphology, state of agglomeration and particle size were observed via SEM(TESCAN VEGA). The average particle size and size distribution were determined by Laser Particle Size Analyzer (OMEC LS900). The crystalline structure was studied by X-ray diffractometer (XRD, DX-1000, DanDong) with Cu Kα radiation. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-11/05/16,10:45:56)

2 234 Eco-Materials Processing and Design XIII 3. Results and Discussion 3.1 Effect of precipitant Lanthanum oxide particles were synthesized using different precipitant respectively, the results were shown in Figure 1. (a) (b) (c) Fig.1 Morphology of La 2 O 3 prepared by different precipitant. (a) ammonium oxalate (b) ammonium bicarbonate (c) aqueous ammonia La 2 O 3 particles with smaller size can be obtained when using ammonium oxalate and ammonium bicarbonate as precipitating. However, they were non-uniform and asymmetry in shape using ammonia from figure 1. La 2 O 3 particles with the smallest, spherical-shaped were synthesized by ammonium bicarbonate. Precursor generated very quickly because ammonia was strong alkaline. It would grow up fast. Reaction between ammonium bicarbonate and Lanthanum nitrate were moderate, then got smaller particles. Therefore, ammonium bicarbonate was selected as precipitating agent in the following experiments. 3.2 Effect of reactant concentration and temperature In order to investigate the effect of reactant concentration and temperature on the size of particles integrated, it adopted the orthogonal experimental method. The details factors and levels were shown in table 1. Experimental conditions and results of analysis were shown in table 2. factor Table 1 The factors and levels of experimental level A:La(NO 3 ) 3 (mol/l) B:NH 4 HCO 3 (mol/l) C:temperature( ) Table 2 The experimental conditions and results No. A:La(NO 3 ) 3 B:NH 4 HCO 3 C:temperature average articles (mol/l) (mol/l) ( ) size(µm)

3 Materials Science Forum Vol Ⅰ Ⅱ Ⅲ Ⅰ/ Ⅱ/ Ⅲ/ average Factors order Ra>Rc>Rb Optimal level A3 B3 C1 Effect of La(NO 3 ) 3 concentration, temperature and NH 4 HCO 3 concentrations on particle size decreased in turn from table 2. Therefore, the optimum process conditions were as follows: concentration of Lanthanum nitrate was 0.18mol/L, concentration ammonium bicarbonate of was 0.6mol/L, reaction temperature was 30 from figure Effect of dispersant agents Table 3 presented the different dispersant agents of Lanthanum oxide nanoparticles synthesis and its effect on the behaviors of La 2 O 3 powder. Table 3 The relationship between average particles size and dispersant agents number dispersant average particles size(µm) 1 PEG n-butanol +PK PEG glycerol 0.43 La 2 O 3 with smallest particle size were synthesized when using PEG20000 as dispersing agent. So PEG was the most adaptive. 3.4 Confirmed experiment using the optimal conditions Morphology of La 2 O 3 powders prepared at optimal conditions was showed in figure 2. Figure 3 was the XRD pattern of La 2 O 3 nanoparticles. All the peaks could be indexed to the hexagonal crystal of Lanthanum oxide. Debye Scherrer formula, L=0.9λ/Bcosθ, had been applied to calculate the size of the nanoparticles. Here L was the coherent length, λ was the wave length of X-ray radiation, B was the full-width at half-maxima of the peak, and θ was the angle of diffraction. The corresponding crystallite size of nanoparticles obtained in this way was 188nm which confirms our findings in SEM image (Fig.2).

4 236 Eco-Materials Processing and Design XIII Intersty (100) (002) (101) (102) (110) (103) (200) (201) Fig. 2 Morphology of La 2 O 3 powders Fig.3 XRD pattern of La 2 O 3 powders prepared at optimal conditions 2θ 4 Conclusions 1) Ammonium bicarbonate and PEG20000 were appropriate precipitation and dispersant respectively. 2) The optimum process conditions were as follows: concentration of Lanthanum nitrate was 0.18mol/L, concentration ammonium bicarbonate of is 0.6mol/L, reaction temperature was 30. The average particles size of Lanthanum oxide powders with spherical shape gained was about 188 nm. Acknowledgements The authors acknowledge the financial support by National Key Technology R&D Program (2009BAA20B02) and Educational Commission of Shaanxi Province of China (12JK0590) References [1] CHEN Hai-song, YU Li-xin, XU Hai-sheng, et al. Marco-kinetics of propane dehydrogenation on Cr-Al catalyst improved by rare-earth aids [J]. J Chem Eng of Chinese Univ, 1999, 13(1): [2] CHEN Zhan-heng. Rare earth new materials and their application in the field of high technology [J].Chinese Rare Earths, 2000, 21(1): [3] Tamai H, Ikeya T, Nishiyama F, et al. NO decomposition by ultrafine noble metals dispersed on the rare earth phosphate hollow particles [J]. Journal of Materials Science, 2000, (35): [4] Weber J K, Richard, Abadie, Johan G, et al. Single phase rare earth oxide-aluminum oxide glasses [P]. US , 2002, [5] McCauley J R, McDaniel J G. Catalyst and process for preparing and using same [P]. USP 6, 117, 813, [6] Bianco, Robert, Buckman, et al. Oxide strengthened molybdenum-rhenium alloy [P]. USP 6, 102, 979, [7] ZHANG Ji-guang, MA Lin, XU Yan. The preparation and characterization of ultrafine Lanthanum oxide by sol-gel process [J]. Journal of Fudan University(Natural Science), 1999, 38(1): [8] ZHANG Mei, YANG Xu-jie, LU Lu-de, WANG Xin. Preparation and characterization of La 2 O 3 nanocrystals [J]. Aerospace Materials & Technology, 1999, (5): [9] YAO Chao, MA Jiang-quan, LIN Xi-ping. The preparation of nanometer lanthanide oxide. Journal of Chemical Engineering of Chinese Universities, 2003, 17( 6) :

5 Eco-Materials Processing and Design XIII / Preparation of Lanthanum Oxide Nanoparticles by Chemical Precipitation Method / DOI References [3] Tamai H, Ikeya T, Nishiyama F, et al. NO decomposition by ultrafine noble metals dispersed on the rare earth phosphate hollow particles [J]. Journal of Materials Science, 2000, (35): /A: [4] Weber J K, Richard, Abadie, Johan G, et al. Single phase rare earth oxide-aluminum oxide glasses [P]. US , 2002, /chin