Synthesis and characterization of Nd 3+ -doped Ce 0.6 Zr 0.4 O 2 and its doping significance on oxygen storage capacity
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Rare Met. DOI 10.1007/s12598-016-0698-3
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Synthesis and characterization of Nd3+-doped Ce0.6Zr0.4O2 and its doping significance on oxygen storage capacity Natesan Shanmuga Priya* S. Kanagaraj
, Chandramohan Somayaji,
Received: 18 August 2015 / Revised: 19 November 2015 / Accepted: 27 January 2016 Ó The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2016
Abstract Cerium and cerium-based oxides are found to be an important element in three-way catalytic converter (TWC). The effective utilization of TWC is found to be reduced due to thermal loading which results in structural deformation of ceria. Doping Zr4? into the rare earth element can increase the oxygen storage capacity and thermal stability. Hence, an attempt was made to study the oxygen storage capacity and thermal stability of ceria by doping Zr4? and Nd3?. Cerium-based nanocrystallite in the composition of Ce0.6Zr0.4-xNd1.3xO2 (0 B x B 0.4) was prepared by sol–gel synthesize technique with citric acid as a gel-forming agent. X-ray diffraction (XRD) result shows that doping Nd3? into ceria lattice forms homogenous solid solution of cubic fluorite structure up to 25 % of substitute only. Doping higher amount of Nd3? into ceria lattice leads to the formation of Nd2O3. Raman spectrum study confirms that oxygen storage capacity band is present in Ce0.6Zr0.4O2 and Ce0.6Zr0.3Nd0.13O2. The oxygen storage capacity was calculated through weight loss of the sample during the second heating cycle with cyclic heating from 30 to 800 °C in thermogravimetric analysis (TGA). The TGA study reveals that the oxygen storage capacity of Ce0.6Zr0.4O2 decreases after the substitution of Nd3?, which is due to the larger ionic radius of Nd3? compared with that of Zr4? and CeO2.
N. S. Priya* Siddaganga Institute of Technology, Tumkur, Karnataka 572103, India e-mail: [email protected] C. Somayaji, S. Kanagaraj Indian institute of Technology, Guwahati 781039, India
Keywords Cerium oxide; Sol–gel technique; Thermogravimetric analysis; Ionic radius; Homogeneous solid solution; Oxygen storage capacity
1 Introduction In recent years, ceria and its oxides have attracted considerable amount of attention as important oxygen storage materials because of its advantages in the field of catalysts. The ability of absorbing/releasing the lattice oxygen reversible with oxygen-rich/oxygen-lean environment is called oxygen storage capacity (OSC). The OSC of ceria makes it not only be used as a catalyst, but also be applied in various fields such as fuel cell [1], oxygen sensor [2], ultraviolet (UV) shielding [3], luminescence [4], surface lapping, and polishing material [5]. The reversible reduction of Ce4? to Ce3? in CeO2 is denoted as redox property, which was found to be responsible for OSC and it would be high at low redox temperature. The cubic fluorite structure of ceria, one of the desirable properties for high OSC, was found to be retained only up to 900 K under reducing atmosphere [6]. The cubic ceria was observed to change it
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