Journal of the European Ceramic Society 37 (2017) 2379–2384 Contents lists available at www.sciencedirect.com Journal of the European Ceramic Society jo ur nal home p ag e: www. elsevier.com/locate/jeurceramsoc Full length article A complex lead-free (Na, Bi, Ba)(Ti, Fe)O 3 single phase perovskite ceramic with a high energy-density and high discharge-efficiency for solid state capacitor applications Anupam Mishra a , Bhaskar Majumdar b , Rajeev Ranjan a,∗ a Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012, India b Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad, 500058, India a r t i c l e i n f o Article history: Received 27 September 2016 Received in revised form 13 January 2017 Accepted 30 January 2017 Available online 5 February 2017 Keywords: Lead free Ferroelectric Energy density Discharge efficiency a b s t r a c t We have investigated a series of compositions in the pseudo-ternary lead-free alloy system Na 1/2 Bi 1/2 TiO 3 -BaTiO 3 -BiFeO 3 with regard to its energy storage density and discharge efficiency. A com- position 0.4(Na 0.5 Bi 0.5 TiO 3 )-0.225BaTiO 3 -0.375BiFeO 3 of this series was identified to give the best energy density and discharge efficiency. While conventional sintering gave energy density of 0.77 J/cm 3 and dis- charge efficiency of 67%, we achieved a remarkable increase in energy storage density (∼1.4 J/cm 3 ) and discharge efficiency (∼90%) by using spark plasma sintering of this composition. Our results suggest that this alloy system can be a potential lead-free candidate for high electric energy storage and discharge efficiency. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction The progress of human civilization in this modern age requires newer sources of energy generation. Developing non polluting techniques for energy generations and finding efficient materials for energy storage are the most discussed topics in this century among the scientific community and global leaders. With active research going on to find new sources of energy, environment friendly energy storage materials also need to be developed [1]. Researchers working in the field of ferroelectrics have off late shown interest in the energy storage aspects of their materials. Lead based ferroelectric materials have shown good energy density and discharge efficiency. However lead is toxic and carcinogenic in nature and has adverse effect on human health and environment. Hence countries are now seriously looking into the aspect of ban- ning the use of lead and laws are being framed for doing so. So there is an increasing pressure on the research community and the industry to find suitable lead free materials which can be used as an alternative to lead based ones in energy storage devices [2–5]. Till date the lead free ferroelectric materials have not shown prop- ∗ Corresponding author. E-mail addresses: rajeev@materials.iisc.ernet.in, ranjan rajeeb@yahoo.com (R. Ranjan). erties comparable to the lead based ones. Anti-ferroelectric and relaxor category of materials are being actively probed for potential applications in energy storage devices owing to their low remnant polarization and coercive field leading to good energy storage capa- bilities and high discharge efficiency. Research groups from across the world are now in the search of suitable lead free materials which can be sintered at low temperature, for better utilization in mul- tilayer ceramic capacitor(MLCC) applications and which displays a good energy density and discharge efficiency [6–8]. A few anti- ferroelectric systems have been reported which have shown good energy storage capabilities and good temperature stability [9,10]. However they lack a high discharge efficiency [11]. Hence a lead free system is required which has both a good energy density and discharge efficiency. Na 0.5 Bi 0.5 TiO 3 (NBT) based system are being seen as the most suitable lead free replacements for the lead based systems. However they have major drawbacks like high dielectric loss, high conductivity and large coercive field which limit their applications [12–15]. Our research was primarily guided by the motivation to find suitable composition in the lead-free category. In this paper we report the results of a pseudo-ternary lead-free alloy Na 1/2 Bi 1/2 TiO 3 -BiFeO 3 -BaTiO 3 . First we identified the optimal composition with best properties by following the conventional ceramic synthesis method. We then investigated the effect of K 0.5 Na 0.5 NbO 3 (KNN) doping in dilute concentration and also com- pare the results vis-à-vis the specimens prepared by spark plasma http://dx.doi.org/10.1016/j.jeurceramsoc.2017.01.036 0955-2219/© 2017 Elsevier Ltd. All rights reserved.