Low cost room temperature curable alumina ink for printed electronic applications Induja I. Jayapalan Nair 1 • Manoj R. Varma 1 • Mailadil T. Sebastian 1,2 Received: 14 March 2016 / Accepted: 22 May 2016 Ó Springer Science+Business Media New York 2016 Abstract A low cost, room temperature curable alumina ink has been prepared by non-aqueous route. The ink is printed on flexible biaxially-oriented polyethylene tereph- thalate (BoPET) substrate as well as on photographic paper. The dielectric constant of the printed alumina on BoPET film is found to be 3.29 and 3.26 at 5 and 15 GHz respectively with a dielectric loss of the order of 10 –3 . The printed alumina layer (without substrate) has a dielectric constant of 4.54 and loss tangent 0.010 at 15 GHz. The temperature coefficient of dielectric constant for alumina ink with BoPET substrate and alumina ink with photo- graphic paper are 60 and 66 ppm/°C respectively. The variation of dielectric constant and loss tangent with the thickness of the printed layer is also investigated. The results indicate that the alumina dielectric ink can be used as a potential candidate for future printed electronic applications. 1 Introduction Printed electronics play a significant role in developing a range of low cost flexible, economically feasible electronic products [1, 2]. Printed electronics allow the combination of electronics with graphic printing. Using this technology, it is possible to manufacture high quality thin, wearable, flexible, light weight, cost-effective and environmentally friendly electronic products [3]. The major fields of applications of printed electronics include RFID tags, sensors, thin batteries, flexible printed wiring boards, light emitting diodes etc. [4]. For realizing this technology, functional inks and efficient printing methods such as screen printing, inkjet printing, gravure, flexographic is adopted [5]. Inks are considered to be the heart of thick and thin film technology [6]. Screen printing or stencil printing is one of the oldest, easiest, cost effective and versatile methods known. It is widely used because of its consis- tency with most of the functional ink as well as substrates and hence is used for printing dielectric as well as con- ducting layers. Screen printing is employed extensively for printing layers having desired thickness particularly in solar cells, fuel cells, sensors, photo catalytic surfaces etc. [7]. The major advantages of screen printing technology are (1) low investment cost, (2) usage of variety of mate- rials, (3) easy mechanization and (4) fast production rate etc. [8]. In screen printing technique, alignment is very crucial because it determines the thickness of the ink and also the uniformity over the area of the surface [9]. The major applications of dielectric inks in hybrid cir- cuits are in insulating multilayer circuits, capacitors, her- mitic seals etc. [10]. Alumina (Al 2 O 3 ) is well known material with excellent dielectric properties, high thermal stability, electrical resistivity, easily available and cost effectiveness [11, 12]. Various organic as well as inorganic additives are needed for the formulation of ink, optimiza- tion of viscosity, stabilization as well as for the drying behavior [1]. A complete understanding of the behavior of the ink is provided by the rheology study [13]. A few commercial dielectric as well as conducting inks are available in the market, and they require high curing & Mailadil T. Sebastian mailadils@yahoo.com 1 Materials Science and Technology Division, National Institute for Interdisciplinary Science Technology, Trivandrum 695019, India 2 Materials Physics and Microelectronics Laboratory, Department of Electrical Engineering, University of Oulu, 90014 Oulu, Finland 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-016-5058-4