ORIGINAL PAPER (Ba 0.93 Nd 0.07 )TiO 3 thin films prepared by sol–gel method as a potential dielectric resonator antenna application Nik Akmar Rejab • Mohamadariff Othman • Wan Fahmin Faiz Wan Ahmad • Mohd Fadzil Ain • Zainal Arifin Ahmad Received: 26 July 2010 / Accepted: 17 September 2010 / Published online: 1 October 2010 Ó Springer Science+Business Media, LLC 2010 Abstract In this paper, we report the application of Neo- dymium (Nd) doped barium titanate thin films (Ba 1-x Nd x ) TiO 3 with x = 0 and 0.07 as dielectric resonator antenna. The films were prepared using the sol–gel method and dip- coating technique. Barium acetate, titanium (IV) isoprop- oxide and neodymium (III) acetate hydrate were used as precursors while glacial acetic acid and acetylacetone were used as solvents. Si wafers were used as a substrate with dipping times varying from 10, 30, and 50 s. The 0.07 films were [ 800 nm thick and crystallized after being annealed at 800°C for 30 min. The films were tested as dielectric reso- nator antenna. It was found that, on the actual antenna circuit, the resonant frequency decreased as the (Ba 0.93 Nd 0.07 ) TiO 3 films thickness increased (from 0.8379, to 5.4525 lm). All samples resonate in the range of 8.68–8.83 GHz with quasi omni-directional radiation patterns. Keywords Barium titanate Á Neodymium Á Sol–gel Á Dielectric Á Resonance frequency 1 Introduction The revolution of using microwaves as the carrier in mobile phone and satellite communication systems has made device miniaturization the biggest challenge to the research and development field [1]. However, the invention of dielectric oxide ceramics concludes the microwave wireless commu- nication industry by reducing the size and cost of filters, oscillators and antenna components in applications ranging from cellular phones to global positioning systems [2]. This invention resulted in the Dielectric Resonator (DR), an electromagnetic component that exhibits resonance with useful properties for a broad range of frequencies. The key properties required for a DR are high dielectric constant (e 0 ), low tangent loss (tan d) and low temperature coefficient (s)[3]. These parameters are related to the size and frequency selectivity in the system. The thin film method is very significant for the miniaturization of microwave devices such as filters, oscillators, and antennas [4]. Previously, several methods for producing BaTiO 3 thin films have been used such as Metal–Organic Chemical Vapour Deposition (MOCVD), sputtering and electropho- retic deposition [5]. Researchers [6–8] reported that sol–gel process powders, fibers and monoliths of ceramic materials can easily be produced, as well as useful complex oxides with the neodymium (Nd) dopant. The sol–gel process, which is also known as chemical solution deposition, is a wet chemical technique widely used in the fields of material science and ceramic engineering. It is a preferred technique because a high purity solution, which is an important advantage of the sol–gel method, can also be produced [9]. Solid state reaction possesses several disad- vantages such as low mixture purity, difficulty in character- ization and also non-homogenous doping distribution. The sol–gel processes are required in producing thin, transparent multicomponent oxide layers of many compositions on various substrates, including glass [5]. In the present study, the effect of Ba 0.93 Nd 0.07 TiO 3 film thickness on the antenna properties were investigated in the N. A. Rejab Á W. F. F. Wan Ahmad Á Z. A. Ahmad (&) School of Materials & Mineral Resource Engineering, Universiti Sains Malaysia (Engineering Campus), 14300 Nibong Tebal, Seberang Perai Selatan, Malaysia e-mail: zainal@eng.usm.my M. Othman Á M. F. Ain School of Electric & Electronic Engineering, Universiti Sains Malaysia (Engineering Campus), 14300 Nibong Tebal, Seberang Perai Selatan, Malaysia 123 J Sol-Gel Sci Technol (2011) 57:172–177 DOI 10.1007/s10971-010-2338-y