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Investigation of Re-Entrant Relaxor Behaviour in Lead Cobalt Niobate Ceramic

23 Pages Posted: 26 Mar 2019 First Look: Accepted

See all articles by Adityanarayan H. Pandey

Adityanarayan H. Pandey

Indian Institute of Technology (IIT), Bombay - Department of Metallurgical Engineering and Materials Science

Surya Mohan Gupta

Homi Bhabha National Institute; Raja Ramanna Centre for Advanced Technology - Laser Materials Processing Division

Abstract

The temperature dependent dielectric properties revealed re-entrant relaxor behaviour (Tm ~130 K and 210 K for 1 kHz) below a high temperature diffused phase transition, Tc ~270 K in lead cobalt niobate (PCN). Multiple positive/negative magnetodielectric effect and deviation from straight line at ~130 K is observed in temperature dependence of inverse susceptibility, which depicts origin of frustration. Microstructure examination depicts closely packed grains with grain size ~8-10 μm and XRD pattern revealed single phase pseudo cubic crystal structure having Pm3m symmetry with lattice constant ~4.0496(2) Å. Rietveld Refinement on XRD data yields larger value of thermal parameters, implying Pb and O are disordered along <111> and <110> directions respectively. Observation of A1g (780 cm-1) mode in Raman spectroscopy and F-spot in SAED pattern along <110> unit axis in TEM suggests presence of nano scale 1:1 Co and Nb non-stoichiometric chemical ordering (CORs), akin to lead magnesium niobate (PMN). K-edge XANES spectra reveals the presence of cobalt in two oxidation states (Co2+ and Co3+); whereas, niobium exists in Nb3+ state. Therefore, these local-average structural properties suggest chemical, structural and spatial heterogeneities. Such multiple heterogeneities are believed to play a crucial role in producing re-entrant relaxor behaviour.

Keywords: Lead cobalt niobate, Relaxor ferroelectrics, Re-entrant relaxor, Transmission electron microscopy, Raman spectroscopy, Non-stoichiometric chemical ordering

Suggested Citation

Pandey, Adityanarayan H. and Gupta, Surya Mohan, Investigation of Re-Entrant Relaxor Behaviour in Lead Cobalt Niobate Ceramic (March 23, 2019). A-19-487. Available at SSRN: https://ssrn.com/abstract=3358876

Adityanarayan H. Pandey (Contact Author)

Indian Institute of Technology (IIT), Bombay - Department of Metallurgical Engineering and Materials Science ( email )

Mumbai, 400076
India

Surya Mohan Gupta

Homi Bhabha National Institute ( email )

Mumbai, MS
India

Raja Ramanna Centre for Advanced Technology - Laser Materials Processing Division ( email )

Indore, 452013
India

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