Structural studies of Mn doped ZnO nanoparticles

https://doi.org/10.1016/j.cap.2010.11.050Get rights and content

Abstract

Mn substituted ZnO nanoparticles with compositional formula Zn1−xMnxO where x = 0.00, 0.04 and 0.08 were synthesized by sol-gel route. All the samples sintered at 650 °C for 12 h in a furnace followed by furnace cooling up to room temperature. X-ray diffraction (XRD) studies shows the presence of hexagonal crystal structure as same as parent compound (ZnO) in all samples. The lattice parameters ‘a’ and ‘c’ were determined from XRD data and found that they increase linearly with the Mn content, which suggests that doped Mn ions go to Zn sites. Grain size, X-ray density and Atomic packing fraction (APF) were evaluated using XRD data and found that grain size increases while X-ray density and Atomic packing fraction (APF) decreases with dopant concentration increases. The functional groups and chemical interactions of Mn substituted Zinc oxide samples were also determined at various peaks using FTIR data and observed the presence of function groups in the samples. Results of such an investigation presented in this paper.

Research highlights

► Mn substituted ZnO nanoparticles synthesized by sol–gel method. ► Maintained wurtzite structure of ZnO upto 8% of Mn doping without any extra peaks of impurities. ► Prominent IR peaks analyzed qualitatively.

Introduction

Diluted Magnetic Semiconductors (DMS) and their nanostructures have attracted lot of attention owing to the combined properties of the magnetic elements and the carriers of the host. In DMS materials, most of studies concentrated on Mn doped II–VI chalcogenide semiconductors and III–V semiconductors [1], [2]. However, the Curie temperatures of these materials above room temperature are predicted if it is doped into p-type. A theoretical prediction, which reveals that hole-mediated Mn doped ZnO and GaN can achieve Curie temperature above room temperature [3]. In Co substituted TiO2 and ZnO system the values of Curie temperature above room temperature were reported [4], [5], [6], [7].

Zinc Oxide is attracting lot of attention of researchers, scientists and technologists owing to its interesting properties like wide band gap of 3.37 ev at room temperature and high exciton binding energy of 60 mev, which makes the exciton state stable even at room temperature [8], [9], [10], [11], [12]. Ferromagnetism is being observed only at low temperatures shown by many research groups. The presence of ferromagnetism in such materials is due to clustering of magnetic ions and impurity phases [13], [14], [15], [16]. Ferromagnetism has been found above room temperature by some research groups for transition metals doped ZnO synthesized by chemical routes [17], [18], [19], [20]. Recently, ferromagnetism has also been observed at room temperature in bulk Mn doped ZnO prepared by solid state reaction method [15]. Zinc Oxide is widely used in a number of applications like photocatalysis, gas sensors, varistors and low voltage phosphor material [21], [22], [23], [24]. With a view to understand the effect of Mn on ZnO, samples have been synthesized by sol-gel route. Our XRD study indicates that no extra peaks present as compared to extra peaks observed in reported literature [25]. FTIR measurement of the spectrum of the samples gives the bands which are in good agreement with the values reported in the literature [26]. Results of such an investigation of Mn substituted ZnO nanocrystalline samples are presented in this paper quantitatively.

Section snippets

Experimental

The samples of Mn substituted ZnO with nominal compositions Zn1−xMnxO (x = 0.00, 0.04 and 0.08) were synthesized by sol-gel route using high purity (99.99% AR grade) acetates of Zn and Mn i.e. Zn (CH3CO2)2 2H2O and Mn (CH3CO2)2 4H2O. The appropriate amounts of Zn and Mn acetates were dissolved in N-dimethylformamide (DMF) in one beaker, stirred for 3 h at room temperature using magnetic stirrer for getting the gel. These gels were heated at 150 °C for 3 h in the furnace then obtained

XRD studies

The X-ray diffraction patterns for all the samples recorded at room temperature are shown in Fig. 1. The analysis of the diffraction peaks revealed the presence of wurtzite (hexagonal) structure phase in all the compositions. No extra peaks of impurity phase were observed in the patterns which indicate that the powders obtained in the present work are single-phase hexagonal ZnO nanoparticles though some extra peaks are shown in the reported literature [25]. The intensity of this peak goes on

Conclusions

The crystal structure of the Zn1−xMnxO compound with x = 0.00, 0.04 and 0.08 synthesized by sol-gel route was studied. From XRD data, it is confirmed that all samples are in the wurtzite ZnO structure. The lattice parameters ‘a’ and ‘c’ increase with the doping percentage of Mn increases which indicates that Mn2+ ions substitute for Zn2+ ions. The grain size, atomic packing fraction and X-ray density were calculated from XRD data. It is found that grain size increases while atomic packing

Acknowledgements

Y. Purushotham wishes to thank Department of Science and Technology (Government of India) for financial support through a Fast Track Project (SR/FTP/ETA-18/2007).

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