Comparative study on structure, dielectric and electrical properties of cobalt- and zinc-substituted Mn 3 O 4 spinels
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Comparative study on structure, dielectric and electrical properties of cobalt‑ and zinc‑substituted Mn3O4 spinels Nayana Acharya1 · Raghavendra Sagar1 Received: 17 September 2019 / Accepted: 21 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper, we report the comparative study of single-phase crystalline M n3O4, CoMn2O4, and Z nMn2O4 spinels prepared by a wet chemical co-precipitation technique. The absence of impurity peaks in the X-ray diffraction pattern of all prepared spinels endorses the formation of highly pure and single-phase spinels with the tetragonal crystal structure. The highest nMn2O4 intensity peak for Mn3O4 was observed at (211) direction plane, and the same was followed by CoMn2O4 and Z with a slight decrease in the angle of diffraction. The microstructure features observed from scanning electron micrographs reveal irregular-shaped nanosized grains with an average grain size of ~ 100 nm. The dielectric studies carried out from room temperature to 500 °C show high dielectric loss at elevated temperatures endorsing better conducting behavior. The DC-conductivity measurement substantiates the negative temperature coefficient of resistance behavior where resistivity decreases with an increase in temperature. The activation energy calculated using Arrhenius relation was 0.58 eV for M n3O4, whereas it is 1.1 and 1.4 eV for Co- and Zn-substituted M n3O4 confirming semiconducting nature of substituted spinels at higher temperature region. Keywords Spinels · Structure · Microstructure · NTCR behavior · Electrical properties
1 Introduction AB2O4-based spinels are one among the most interesting structural ceramic compositions due to their wide ranging application in energy storage, sensor systems, magnetic data storage, catalysis, etc. A B2O4 structure consists of a divalent ion in A (tetrahedral) site and di- or trivalent ions in B (octahedral) site [1–4]. Among many spinels, manganese-based spinels have attracted great attention due to their significant use in commercial negative temperature coefficient (NTC) thermistors [5]. Also, manganese-based spinels are extensively probed for their potential use in applications such as protective coatings for SOFC interconnects, electrodes for supercapacitors, catalysts and gas sensors due to their high temperature sensitivity, swift response and low cost [6]. Mn3O4 attracts huge attention due to its tunable chemical and physical properties, which mainly depend on slight * Raghavendra Sagar [email protected] 1
Department of Physics, Mangalore Institute of Technology and Engineering Badaga Mijar, Moodbidri, Dakshina Kannada, Karnataka 574225, India
variation in lattice parameters of crystal structure and grain size [7–9]. However, its structural stability could be easily distorted with a small variation in temperature. The substitution of homo- or hetero-valance ions in M n3O4 is one of the most common and simplest ways to improve structural stability against any small variation in temperat
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