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Kelsey Coolahan and Samuel E. Lofland Department of Physics and Astronomy, Rowan University, Glassboro, New Jersey 08028 (Received 26 January 2013; accepted 12 March 2013)

A simple and modified solvothermal method using oxalate precursor, used to synthesize Cd1
xNixO (x 5 0.047, 0.102, and 0.163) nanoparticles and their phase structure, morphology, optical and magnetic properties, have been investigated. X-ray diffraction studies revealed that asprepared Ni-doped CdO solid solutions are highly crystalline and stabilized in a monophasic cubic CdO structure. X-ray diffraction and ICP-MS studies confirmed the incorporation of Ni21 in a CdO matrix. The average grain size was found to be 30, 15, and 11 nm, respectively, using transmission electron microscopic studies. High surface area in the range of 118–143 m2/g has been achieved for these solid solutions using the multipoint BET method, which increases on increasing Ni concentration in Cd lattice site. The optical band gap of these solid solutions shows red shift to the undoped CdO. Ni-doped CdO nanoparticles exhibit co-existence of paramagnetism and ferromagnetism.

I. INTRODUCTION

Nanomaterials of conducting oxides have attracted the attention of researchers over the last two decades due to their outstanding applications in solar cells, flat panel displays, photovoltaic devices, smart windows and optical transmission devices.1–4 Though CdO was the first reported transparent conducting film,5 it has not been extensively studied compared to other oxides like tin dioxide (SnO2), zinc oxide (ZnO) and indium oxide (In2O3) due to its relatively small band gap. However, recently, CdO based transparent conducting oxides have shown keen interest due to their relatively simple crystal structure, high carrier mobilities and nearly metallic conductivities.6–9 The band gap of bulk CdO is relatively small, which may lead to the poor optical transparency in short wave length range, thus the physical properties of CdO could be controlled for optoelectronic applications by doping with ions like In,10–13 Sn,1,4 Al,14 Sc,9 and Y,15 which improves its n-type conductivity and increases the optical band gap. Considering the potential applications of CdO, metal doped CdO has stimulated considerable research effort. Therefore, many researchers have investigated the structural and optical properties of various transition elements (In, Sc, Y, Al, Sn, Fe, and Ga) doped CdO.1,4,10–17 The entire range of bulk Cd1
xCaxO (0 # x # 1) has been synthesized and showed wide band gap tunability.18 a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.69 J. Mater. Res., Vol. 28, No. 9, May 14, 2013

http://journals.cambridge.org

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However, very few reports are available in the literature for the synthesis of Ni-doped CdO. Recently, Cd1
xNixO (x 5 0.02, 0.04, 0.06, and 0.08) thin films have been synthesized using a sol-gel based spin coating method in which the increase in band gap was observed (2.26– 2.60 eV) with decrease in the grain size (8