Journal of Alloys and Compounds 536S (2012) S511–S515 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds jou rn al h om epage: www.elsevier.com/locate/jallcom Dielectric properties of Bismuth Titanate densified by Spark Plasma Sintering and Pressureless Sintering Joel O. Herrera Robles a , Claudia A. Rodríguez González a , Sebastián Díaz de la Torre b , Luis E. Fuentes Cobas c , Perla E. García Casillas a , Hector Camacho Montes a,* a Basic Science Department, IIT, Universidad Autónoma de Ciudad Juárez, Av. del Charro 460 norte Cd. Juárez, Chih., C.P. 32310, Mexico b Instituto Politécnico Nacional, Centro de Investigación e Innovación Tecnológica CIITEC, Azcapotzalco, México, D.F., C.P. 02250, Mexico c Centro de Investigación en Materiales Avanzados CIMAV, Complejo Industrial, M. Cervantes 120, Chihuahua, C.P. 31109, Mexico a r t i c l e i n f o Article history: Received 23 June 2011 Received in revised form 19 December 2011 Accepted 9 January 2012 Available online 15 January 2012 Keywords: Bismuth Titanate ceramics SPS and PLS sintering Dielectric properties a b s t r a c t Bismuth Titanate powder Bi 4 Ti 3 O 12 of 175 nm mean particle size has been synthesized through chem- ical precipitation and calcination of chemical precursors at 700 ◦ C. Ceramic pellets were sintered by conventional Pressureless Sintering (PLS) and Spark Plasma Sintering (SPS) techniques. SPS is shown to be effective in inhibiting grain growth and allowing the formation of a homogeneous microstructure. The optimum SPS temperature is 800 ◦ C in less than 5 min. PLS specimens seem to be more sensible to temperature rise and sintering time, undergoing grain grow and plates-like morphology. This fact leads formation of a given crystallographic texture. Dielectric properties of SPS specimens are found dependent of the electric signal frequency and less sensitive to sintering temperature than PLS counterparts. © 2012 Elsevier B.V. All rights reserved. 1. Introduction In spite of first time has being studied in 1949 [1], the Aurivillius phase was extensively investigated in the last two decades. Among the materials that exhibit such phase, special attention deserves the Bismuth Titanate, Bi 4 Ti 3 O 12 [2–7] compounds having fine grain microstructure. Nanostructured materials constitute a relatively new trend and alternative option on searching for advanced mate- rials of improved properties [8]. Thus, the combination of chemical routes to obtain nano-sized powder and rapid sintering methods is a promising ceramic processing alternative for Bismuth Titanates [9–15]. In this work the authors have conducted a series of exper- iments through which after obtaining fine ceramic powder via chemical co-precipitation, a comparison has been made on PLS- and SPS-sintering techniques as to investigate the final dielectric properties of thus sintered pellets and have tried to relate this information with attained microstructures. 2. Experimental procedure Bismuth Titanate powder was obtained by chemical co-precipitation route start- ing from bismuth nitrate Bi(NO3)3·5H2O, 99% pure and titanium tetra-n-butoxide Ti(O-n-C4H9)4, 99% pure commercially available from Alfa Aesar. Further details on their preparation procedure can be found in literature [9,10]. The resulting * Corresponding author. Tel.: +52 656 6884887. E-mail address: hcamacho@uacj.mx (H. Camacho Montes). precursors were fired in a conventional electric furnace under air atmosphere at 700 ◦ C for 180 min. Processed powder was characterized using X-ray diffrac- tion analysis XRD supplied with a Panalytical X’pert Pro. (Panalytical, Eindhoven, Netherlands) with source of X-rays is Cu K-alpha (wavelength 1.540598 ˚ A). Obtained powder was then sintered by the Pressureless Sintering (PLS) technique at 850, 950, and 1000 ◦ C, for 600, 540 and 360 min, respectively. These time intervals for each temperature were selected with the purpose of reaching a relative density of at least 90% and minimize any possible bismuth volatilization. The Spark Plasma Sin- tering (SPS) was also used. This experimental runs were carried out using 5 g of powder, applying 500 A, pulse switch on/off 12/2, and 10 kN load. The heating rate was set to 100 ◦ C/min until reaching 750, 800 and 1000 ◦ C. Sintered pellets were characterized by XRD and scanning electron microscopy SEM analyses, using a SEM model JSM-7001F (Jeol, Tokyo, Japan). The real dielectric constant and the loss tan- gent were measured with an Agilent 4285-A precision LCR-meter apparatus (Santa Clara, CA, USA). Real dielectric constant component, ε ′ (ω), describes the capacity to storage electric field energy and the imaginary dielectric constant component, ε ′′ (ω), describes the capacity to transform electric field energy into heat. The loss tangent is defined as ı = ε ′′ (ω)/ε ′ (ω). 3. Results and discussions In order to assure formation of the Aurivillius pure phase the firing temperature was systematically deduced after several heat treatments, leading us to 700 ◦ C for our Bi 4 Ti 3 O 12 powder. This powder attained a mean particle size of 175 ± 48 nm, as deduced from SEM analysis in Fig. 1. The particle size was measured using the software Scandium which is an Olympus Soft Imaging Solu- tions’ image analysis platform for scanning electron microscopy (Lakewood, CO, USA). 0925-8388/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2012.01.053