International Journal of All Research Education and Scientific Methods (IJARESM), ISSN: 2455-6211 Volume 9, Issue 1, January -2021, Impact Factor: 7.429, Available online at: www.ijaresm.com IJARESM Publication, India >>>> www.ijaresm.com Page 1514 Optical and Photoluminescence Properties of Zn 1-X cd x o Nanoparticles Synthesized by Sol-Gel Method T. Mohan Kumar 1 , Y. Vasudeva Reddy 2 , M. Nagabhushanam 3 1,3 Department of Physics, Osmania University, Hyderabad-500007, Telangana, India. 2 Department of Physics, Government City College (A), Hyderabad500002, Telangana, India -----------------------------------------------------------*****************--------------------------------------------------------- ABSTRACT Zn1-xCdxO (x=0, 0.02, 0.04, 0.06) nanoparticles have been synthesized by sol–gel method. X-ray diffraction studies revealed that the powders possess Hexagonal Wurtzite phase. Rietveld refinement showed a significant change in lattice parameters of Zn1-xCdxO compounds with cadmium concentration. The optical band gap, estimated from Ultraviolet-Visible Spectroscopy study, decreased from 3.22 to 3.15 eV with the increase in cadmium content. The photoluminescence spectrum exhibited three different emission bands around 410 nm, 460 nm and 510 nm. The broadness of strong green emission peak was observed to increase with cadmium concentration. All the luminescence peaks are explained as due to various defects like zinc vacancy (VZn), oxygen vacancy (VO), zinc interstitial (Zni) and their complexes. Keywords: Doped ZnO, Sol-gel method, Rietveld Refinement, Optical Transmittance, Photoluminescence. INTRODUCTION Investigations, in the recent past, were focussed in developing new nano-semiconductor material and search for efficient ways to tailor their optical properties because optical applications of conventional semiconductor material were limited in view of their fixed energy gap. In this regard, studies on wide band gap semiconductors such as ZnSe, GaN and ZnO based materials have progressed substantially [13]. Among these material, ZnO is an n-type compound semiconductor with direct band gap of 3.37 eV (bulk) and large exciton binding energy 60 meV at room temperature which is approximately three times greater than that of ZnSe and GaN [24]. Therefore, it attracted considerable amount of research interests on ZnO due to its excellent electrical, optical, outstanding thermal properties and chemical stability [1,5]. ZnO nanoparticles have been extensively studied owing to its high technological applications in optoelectronic devices [1,6], gas sensors [7], solar cells [89], photo-detectors [10], light emitting diodes (LEDs) [11,12] and laser diodes [12,13]. In general, the properties semiconductors can be improved further, doping was considered as one of the effective ways. Rare earth and/or transition metal ions are good candidates for doping in order to tune the optical properties of the material [2,45,11]. Introduction of such impurities can modulate the optical properties of semiconductors with or without changing the structure of the host [1415]. In this context, one or two elements like Al, Ba, Ca, Cd, Co, Cu, Fe, Li, Mn, Mg, Na, Ni, are used as doping agents to tune the optical properties of ZnO. Unlike the other elements, it is observed that the influence of cadmium on ZnO is less discussed in the literature. When ZnO is doped with Cd 2+ ions, it can substitute Zn 2+ site or go to an interstitial site of the host ZnO lattice. Furthermore, in case of substitution, a lattice distortion and expansion / contraction may occur due to the difference in their ionic radii. In the present case, ionic radius of Cd 2+ (0.74Å) is greater than that of Zn 2+ (0.60 Å) [1617], it may therefore cause expansion in the dimensions of crystal lattice and may cause changes in the optical properties of the material by altering their energy gap. To fabricate an optical device, tuning of energy gap is necessary and ZnCdO is considered as one of the ideal material among ZnO based materials [4 5]. Hence, Cd doped ZnO nano material have attracted much attention of many researchers. Consequently, electrical and optical studies have been made on Cd doped ZnO thin films [45, 1722] but there are very few reports on optical studies of Cd doped ZnO nanoparticles [2326].