Sol-gel auto combustion synthesis, electrical and dielectric properties of Zn 1x Co x O (0.0  x  0.36) semiconductor nanoparticles Shankar D. Birajdar a , Pankaj P. Khirade a , Tukaram S. Saraf a , R.C. Alange b , K.M. Jadhav a, * a Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, M.S, India b Department of Physics, Shri. Madhavrao Patil Mahavidyalaya, Murum, Osmanabad, M.S, India article info Article history: Received 14 May 2016 Received in revised form 26 July 2016 Accepted 22 August 2016 Available online 24 August 2016 Keywords: XRD TEM SAED Dielectric properties abstract In the present work, Co 2þ ion doped zinc oxide nanoparticles Zn 1x Co x O (x ¼ 0.00, 0.06, 0.12, 0.18, 0.24, 0.30 and 0.36 mol) were synthesized by sol-gel auto combustion method. The effects of heavily doped Co 2þ ion concentration on the structural, electrical and dielectric properties were studied. The prepared nanoparticles were characterized by X-ray diffraction technique (XRD), transmission electron microscopy (TEM), selected area diffraction pattern (SAED) and Fourier transform infrared spectroscopy (FT-IR). The X-ray diffraction analysis revealed the formation of single phase having hexagonal wurtzite structure along with secondary phase (Co 3 O 4 ). TEM analysis clearly showed the small agglomeration and spherical shape of nanoparticles. SAED pattern also confirms the hexagonal wurtzite structure with single crys- talline nature. FTIR analysis showed the vibrational frequency band position of ZneO shifted to higher frequency band with Co 2þ ion increasing host semiconductor nanoparticles. The temperature dependent (300e400 K) DC resistivity of samples was studied by the standard two probe method. DC electrical resistivity was found to increase with increasing Co 2þ content in ZnO matrix. The dielectric properties of pure and Co 2þ doped ZnO nanoparticles were studied as a function of frequency and composition using the LCReQ meter. All the dielectric parameters show dispersion and decreases with increase in Co 2þ content. The observed dielectric behavior is explained on the basis of MaxwelleWagner model and Koops phenomenological theory. © 2016 Elsevier B.V. All rights reserved. 1. Introduction The group IIeVI (ZnS, ZnO, CdS and CdO) semiconductor nanoparticles have attracted a lot of attention due to their unique magnetic and optical properties for spintronic and optoelectronic device applications [1,2]. Because of excellent optical and magnetic properties, IIeVI semiconductor nanoparticles find a broad range of potential applications in today's technology such as light-emitting diodes, solar cells and optical devices based on the nonlinear op- tical properties [3e5]. Among the group IIeVI semiconductor, zinc oxide, an important semiconductor material, has considerable in- terest because of their remarkable properties such as Curie tem- perature at room temperature, wide band gap energy (3.30 eV) at room temperature [6] and high excitonic binding energy (60 meV) [7], n-type semiconductor material, which can be used for application of optoelectronic device, especially for ultraviolet (UV) light-emitting diodes (LEDs) and laser diodes (LDs) [2]. ZnO is a non-magnetic (diamagnetic) semiconductor material, when a small fraction of magnetic metal ion such as Co 2þ , Ni 2þ and Fe 2þ doped in non magnetic semiconductor material, then diamagnetic material shows ferromagnetic properties, which is called dilute magnetic semiconductor material (DMS) [8], consequently, ZnO is a potential candidate for spintronic device applications [9]. Doping is one of the effective ways to modify the properties of host material for preferred applications. Doped materials show different type of magnetic and optical properties, which strongly depend on the type of dopant ions. These dopant impurities play a crucial role in changing the electronic structure of the host material. Addition of impurities to ZnO lattice often induces dramatic changes in the structural, electrical, optical and magnetic properties of host ma- terial. There are many reports on the optical and magnetic prop- erties of ZnO nanostructures doped with various kinds of impurities like Cu 2þ , Mn 2þ , and Co 2þ [10e12]. In particular, when doped with magnetic metal ions (e.g. Co 2þ , Ni 2þ , Fe 2þ ), these ma- terials can produce unique magnetic and magneto-optical * Corresponding author. E-mail addresses: shankarbirajdar2013@gmail.com (S.D. Birajdar), drjadhavkm@ gmail.com (K.M. Jadhav). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom http://dx.doi.org/10.1016/j.jallcom.2016.08.220 0925-8388/© 2016 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 691 (2017) 355e363