Influence of liquid phase lead borate glass on dielectric response of lead iron niobate Tanveer Quazi a,⇑ , Kamal Singh b , Shahin Sayyed b , S. Acharya b a Anjuman College of Engineering & Technology, Nagpur 440001, M.S., India b Department of Physics, Rashtrasant Tukdoji Maharaj Nagpur University, Nagpur 440033, M.S., India article info Article history: Received 30 May 2013 Received in revised form 14 October 2013 Accepted 15 October 2013 Available online 26 October 2013 Keywords: Ferroelectrics Sintering Dielectric response Scanning electron microscopy (SEM) abstract Lead iron niobate Pb Fe þ3 1=2 Nb þ5 1=2   O 3 h i (PFN) is well recognized lead-based complex-double perovskite [A(B I B II )O 3 ] ferroelectrics. In the present work, the influence of liquid phase of lead borate glass 4PbO-B 2 O 3 (LB) on sinterability and dielectric behaviours of PFN are systematically investigated. The PFN powder was synthesized by combustion route (SHS synthesis) and LB-glass by conventional quench- ing technique, separately. The compositions of PFN and LB-glass (0–3 wt%) were prepared by ball milling. The crystalline structure of as-synthesized PFN, PFN–LB and amorphous nature of LB-glass are confirmed by XRD and well fitted by Rietveld refinement with monoclinic structure of ‘Cm’ space group. Microstruc- ture was examined by SEM and TEM; indicates nanoscale dimensions of as-synthesized PFN. The green pellets of PFN and PFN–LB were sintered at various sintering conditions. Liquid phase sintering by LB- glass in PFN is found to strongly influence on the morphology, compactness and dielectric behaviour of nanostructure PFN. Semiquantitative correlation between microstructure and dielectric behaviour was established. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Lead iron niobate Pb Fe þ3 1=2 Nb þ5 1=2   O 3 h i (PFN) is belongs to lead- based complex-double perovskite [A(B I B II )O 3 ] ferroelectric family. It was found most attractive due to their exceptionally high dielec- tric constant for making multilayer ceramic capacitor [1–3]. Suit- ability of PFN to yield cost effective multilayer capacitors has been realized by lowering the sintering temperature (<1000 °C); it makes to use non-noble inexpensive materials (viz., 70:30 Ag: Pd, etc.) as electrode for multilayer capacitor [4–6]. A diffuse phase transition (DPT) with a non-relaxor type behaviour has been ob- served in PFN [7]. This makes the research on PFN-system more attentive and attempts have been mostly focused on development of high quality PFN-based system having low sintering tempera- ture with enhancing dielectric constant, less loss and controlling lead loss during processing [8–12]. Optimizing processing condi- tions to obtain high quality PFN for device application is a major challenge. Recent literature reveals that the liquid phase sintering (LPS) of ceramic using B 2 O 3 , Bi 2 O 3 , LiF, etc as sintering aids has been found to be a highly effective way to decrease sintering temperature with improving dielectric constant and minimizing lead loss during sintering [13–16]. In general, liquid phase sintering in ceramics has been observed to induce complete densification at much lower temperature [17–19,15]. In addition to that, enhancement in dielectric and piezoelectric properties of ceramics has been re- ported in very few cases by liquid phase sintering [20–27]. A systematic review of recent literatures on use of glass as sin- tering aids to improve sinterability and dielectric behaviour in fer- roelectric ceramics is given in Supplementary data file-1. Amongst the available glasses system, PbO-based glasses have been ob- served to have lowest softening temperature, around 500 °C, high ionic polarizability and low dielectric losses and thus are more appropriate for liquid phase sintering [16,28]. With this motivation, in the present work, PbO-based glass are selected as sintering aids in the PFN double perovskite system. Structure is confirmed by X-ray diffraction study. Microstructures are examined by SEM and TEM. Sinterability of the PFN–LB system is systematically investigated by using liquid phase sintering and results are compared with pure PFN system. Effects of liquid phase sintering on dielectric behaviour are investigated. Semiquantita- tive correlation between microstructure and dielectric behaviour is established. 2. Experimental The initial ingredients used in this work were Pb(NO 3 ) 2 (99% Merck), Fe(NO 3 ) 3- 9H 2 O (99% Merck) and Nb 2 O 5 (99.5 Sigma–Aldrich) as cation precursors and urea, CO(NH 2 ) 2 (99% Merck) as a fuel. The precursor were initially mixed in 50 ml distilled 0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.10.114 ⇑ Corresponding author. Tel.: +91 09326449300. E-mail address: tanveerquazi05@gmail.com (T. Quazi). Journal of Alloys and Compounds 587 (2014) 26–31 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom