Structural, optical, and low-temperature resistivity of Ca-doped PrMnO 3 nanoparticles
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ORIGINAL ARTICLE
Structural, optical, and low-temperature resistivity of Ca-doped PrMnO3 nanoparticles Satyam Kumar 1 & Indrasen Ram 2 & Aditya Kumar 3 & Upendra Kumar 4 Received: 17 August 2020 / Accepted: 21 September 2020 # Qatar University and Springer Nature Switzerland AG 2020
Abstract The different Pr0.7Ca0.3MnO3 (PCMO) nanoparticles (NPs) with average particle size ranging from 46 to 80 nm were prepared through the sol-gel process at 600 °C, 800 °C, and 1000 °C. To check the effect of temperature on Pr0.7Ca0.3MnO3 NPs, we have performed structural, transport, and optical properties. The particle size found increases with sintering temperature due to increasing crystallization. Raman spectrum analysis of all NPs does not show any phase shift with increasing temperature. FTIR spectroscopy studies show the presence of vibration of Mn–O around 600 cm−1 indicated the formation of phase PrMnO3. UV-Vis study of the samples illustrated a wide bandgap semiconducting nature of sample. Two types of conduction mechanisms are observed: thermally activated process in high-temperature region and variable range hopping (VRH) in low-temperature region, which further supports the delocalization of electrons between the multivalent sites of Mn, in the nanocrystalline system. Keywords Perovskite . Sol-gel . XRD . Raman . Variable range hopping
1 Introduction The perovskite has general chemical formula ABO3, where A and B are two cations selected in such a way that the total charge obtained from cations is compensated by charge of oxygen ions. The rare earth (e.g., La3+, Pr3+, Nd3+, etc.)–based manganite RMnO3 oxides modified by alkaline earth (e.g., Ca2+, Sr2+, Ba2+) have been widely studied for semiconductor device, luminescence, and magnetic device applications [1]. Thus, they are used as key materials in the field of gas sensing [2–4], photocatalyst [4, 5], and magnetic storage devices [6] and as light modulators in optical instruments [7]. In manganite oxides, the presence of Mn in multivalent states such as Mn 2+ , Mn 3+ , and Mn 4+ gives wide spectrum for the
* Upendra Kumar [email protected] 1
Department of Physics and Electronics, Hansraj College (University of Delhi), Delhi 110007, India
2
Department of Physics, Dayal Singh College University of Delhi, New Delhi 110007, India
3
Centre of Material Sciences, University of Allahabad, Allahabad 211002, India
4
Department of Physics, Banasthali Vidyapith, Rajasthan 304022, India
conduction of electron as well as defects like oxygen vacancies migrating via the grains, which explored for the application in electrode materials for solid oxide fuel cell (SOFC) [8–10]. Also, the presence of Mn in multivalent states in manganite oxides attracted researcher’s attention due to their exciting features, i.e., colossal magnetoresistance (CMR), superconductivity, and ferroelectricity in terms of charge ordering (CO), Jahn-Teller (J-T) effect, polaron model, and double exchange (DE) [2, 11, 12]. Both theory and experiment have manifested that charge ordering shows ph
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