Effect of alkaline excess on sintering, microstructural, and electrical properties of Li 0.12 Na 0.88 NbO 3 ceramics Supratim Mitra 1,3, *, Pankaj K. Patro 2 , and Ajit R. Kulkarni 1 1 Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076, India 2 Powder Metallurgy Division, Materials Group BARC, Vashi Complex, Navi, Mumbai, India 3 Present address: NIIT University, Neemrana, Rajasthan 301705, India Received: 7 May 2016 Accepted: 20 June 2016 Published online: 29 June 2016 Ó Springer Science+Business Media New York 2016 ABSTRACT Sintering behavior in Li 0.12 Na 0.88 NbO 3 (LNN-12) ceramics has been investigated by analyzing the microstructures of the samples sintered at different tempera- tures (1050–1250 °C) and durations (1–6 h) to optimize the sintering conditions. An excess amount of Li 2 CO 3 was added (1, 3, 5 mol%) to stoichiometric LNN-12 in order to compensate for the probable alkaline element loss at higher opti- mized sintering temperature. The addition of excess Li 2 CO 3 into the starting materials and the effect of it on microstructure and electrical properties were investigated. Microstructural study of Li 2 CO 3 -added samples revealed abnor- mal grain growth, a characteristic feature of liquid phase sintering due to the low melting Li 2 CO 3 . The temperature and frequency dependence of dielectric constant shows two phase transitions in temperature dependence and low-fre- quency dispersion in the frequency dependence of dielectric plot. The observed frequency dispersion is attributed to dominant DC conductivity. The conduction mechanism was identified as diffusion of intrinsic Li ? ion. The room-tempera- ture dielectric constant and loss factor were found to increase with increase in Li 2 CO 3 addition from 160 to 690 and 0.02 to 0.04, respectively. The electrical conductivity was found to increase two orders of magnitude (10 -12 – 10 -10 X -1 cm -1 ) in Li 2 CO 3 -added samples as compared to stoichiometric com- position. The results obtained here give a strong evidence of the stoichiometry– microstructure and electrical properties correlation, thus emphasizing on the importance of processing parameters to tune the desired properties in Li 0.12 Na 0.88 NbO 3 ceramics. Address correspondence to E-mail: supratimmitra2003@gmail.com DOI 10.1007/s10853-016-0156-5 J Mater Sci (2016) 51:9031–9042