Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Dose dependent modifications in structural and magnetic properties of γ- irradiated nanocrystalline Mn 0.5 Zn 0.5 Fe 2 O 4 ceramics V. Jagadeesha Angadi a , A.V. Anupama b , R. Kumar b , H.M. Somashekarappa c , S. Matteppanavar a , B. Rudraswamy a , B. Sahoo b, ⁎ a Department of Physics, Bangalore University, Bangalore, Karnataka 560056, India b Materials Research Centre, Indian Institute of Science, Bangalore 560012, India c Center for Application of Radioisotopes and Radiation Technology, Mangalore University, Mangalore 574199, India ARTICLE INFO Keywords: Mn-Zn ferrite Nanocrystalline Ceramics γ-irradiation Phase transformations Mössbauer spectroscopy ABSTRACT Different doses of γ-radiation can be used to modify the structural and magnetic properties of a host of materials. The Mn 0.5 Zn 0.5 Fe 2 O 4 ceramics samples prepared by the solution combustion route were exposed to different doses of γ-radiation in order to study stability and phase transformations. The creation of defects and building up of strain was observed after medium doses of γ-irradiation (up to 25 kGy) into the single phase pristine samples. However, after 50 kGy of γ-irradiation the locally generated heat drives atomic diffusion, as indicated by the morphological changes in the sample. Furthermore, the sample decomposed into two new stable crystalline phases, α-Fe 2 O 3 and ZnFe 2 O 4 , along with amorphous MnO phase. Besides the structural transformations we have observed the deterioration of magnetic properties at higher doses. Our results are important for understanding the stability and performance of the ferrite based devices used near intense high energy radiation sources. 1. Introduction The Mn-Zn ferrites are potentially attractive materials for techno- logical applications due to their high electrical resistivity, high satura- tion magnetization, high permeability and low coercivity, leading to low power losses [1–9]. The applications of Mn-Zn ferrites include their use as transformer cores, electromagnet cores, in microwave and computer technologies, etc. [1–3]. Improvement of the properties of these materials is important to tune the performance and efficiency of devices. Recently, γ-irradiation was used to modify the properties of ferrite materials [10–13]. The γ-irradiation can be an effective tool to enhance crystallographic defects and to tune the properties of ferrites [13] in a controllable way. Hence, the γ-irradiation induced defect creation and modifications in structural, electrical and magnetic properties of ferrites have attracted a lot of scientific attention. These changes can be ascribed to the breakdown of ferrimagnetic order, surface state pinning and cation inversion, etc. [10,11]. Quantitatively, these changes are functions of γ-irradiation dose rate, time and absorption by the materials etc. Recently, the effect of γ-radiation on the structure, electrical and magnetic properties of Co–Zn ferrites [11], Co 0.6 Zn 0.4 Mn x Fe 2-x O 4 [12], Ni–Zn spinel ferrites [13–15] and CoFe 2 O 4 [16] were studied. The effect of very low dosage of gamma irradiation (5, 100 and 200 Gy) on Mn-Zn ferrites is also reported [17,18]. However, a systematic study on the effect of high dose ( > 200 Gy) gamma irradiation induced phase transformations is not investigated. Herein, we report the effect of γ- radiation dose dependent changes in morphological, structural and magnetic properties of Mn 0.5 Zn 0.5 Fe 2 O 4 nanoferrite. 2. Materials and methods Nanocrystalline Mn 0.5 Zn 0.5 Fe 2 O 4 ceramic powder was synthesized by solution combustion route as described earlier [7]. The powder was pressed into pellets and exposed to γ-radiation (from a 60 Co-radiation source, dose rate of 9.5 kGy/h, (1 Gy=1 J/kg)) for 95, 160 and 315 min leading to a total dose of 15, 25 and 50 kGy, respectively. For the pristine sample and the samples after γ-irradiation dose of 15, 25 and 50 kGy we have used the sample codes: Z3, IZ3-15, IZ3-25 and IZ3-50, respectively. The structural parameters like lattice constant, phase composition and cation distribution were obtained by the Rietveld refinement of the XRD patterns (Fig. 1) for all the samples. The structural parameters, average crystallite sizes and lattice strains determined using Williamson-Hall method are given in Table 1. The Mössbauer spectra http://dx.doi.org/10.1016/j.ceramint.2016.09.188 Received 10 August 2016; Received in revised form 26 September 2016; Accepted 27 September 2016 ⁎ Corresponding author. E-mail address: bsahoo@mrc.iisc.ernet.in (B. Sahoo). Ceramics International 43 (2017) 523–526 0272-8842/ © 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Available online 28 September 2016 crossmark