Preparation of lanthanum tungstate membranes by tape casting technique Manuel Weirich, Jonas Gurauskis*, Vanesa Gil, Kjell Wiik, Mari-Ann Einarsrud Department of Materials Science and Engineering, Norwegian University of Science and Technology, Sem Sælandsvei 12, NO-7491 Trondheim, Norway article info Article history: Received 14 August 2011 Received in revised form 13 September 2011 Accepted 14 September 2011 Available online 17 October 2011 Keywords: Lanthanum tungstate Tape casting Porosity Membrane abstract Lanthanum tungstate materials have been reported to show exceptional mixed proton and electron conducting behaviour at elevated temperatures and making them attractive for dense hydrogen gas separation membranes. In this work preparation of planar asymmetric lanthanum tungstate membranes was addressed. For this purpose carbon black and rice starch pore formers were evaluated for optimum substrate gas permeability. It was found that carbon black pore former results in higher level of effective porosity. Stabilization of fine lanthanum tungstate powder in ethanol based solvent media was carried out to find out optimum surfactant quantity for tape casting slurry. By combining lanthanum tung- state tapes with and without pore former defect free asymmetric membranes were produced by conventional sintering. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Conventional methods used for pure hydrogen gas produc- tion/separation will not meet the emerging hydrogen market needs due to price and sustainability requirements [1]. One of the promising alternatives is the use of dense ceramic membranes [1e3]. These membranes present mixed electron and proton conducting behaviour and can selectively separate hydrogen at elevated temperatures without the need of any external electric circuits. Although the research on dense hydrogen gas separation membranes has been carried over many years, only few compositions have been found which present sufficient flux and make them reliable for industrial scale applications [3]. Oxides of the lanthanum tungstate family with the formula LaW 1/6 O 2 have been reported to show exceptional proton conductivity of w5  10 4 S/cm at 400  C [4] and peaking up to w5  10 3 S/cm at 900  C [5] under wet conditions. Furthermore, these oxides exhibit ambipolar protoneelectron conductivities at temperatures above 800  C [4,6] making them attractive selection for hydrogen gas membrane applications. Thus there has been growing interest from the scientific community to evaluate the stability of this material and possible employment in hydrogen gas separation systems [5,7,8]. It is well known that apart from compositional depen- dence the permeability of gas through the dense membrane can be improved by architectural arrangement. By simply decreasing the membrane thickness, the bulk diffusion contribution can be reduced improving the gas flux. However a reduction in membrane thickness below 100 mm prompts the use of a support layer due to structural performance conditions. This leads to an asymmetric-structured membrane architecture composed of a thin dense func- tional layer and porous structural support which should meet the following requirements: * Corresponding author. Tel.: þ47 73594079. E-mail address: jonas.gurauskis@material.ntnu.no (J. Gurauskis). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 8056 e8061 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.09.083