Revista Română de Materiale / Romanian Journal of Materials 2012, 42 (3), 299 – 305 299 FILME SUBŢIRI PE BAZĂ DE TANTALAT DE BARIU ŞI MAGNEZIU OBŢINUTE PRIN PROCESARE SOL-GEL BARIUM MAGNESIUM TANTALATE THIN FILMS OBTAINED BY SOL-GEL PROCESSING CRISTINA BUSUIOC 1, 2∗ , SORIN ION JINGA 1 , ECATERINA ANDRONESCU 1 1 Universitatea “Politehnica” Bucureşti, Str. Gh. Polizu, nr. 1-7, 011061, Sect. 1, Bucureşti, România 2 Institutul Naţional pentru Fizica Materialelor, Str. Atomiştilor, nr. 105bis, 077125, Măgurele, Jud. Ilfov, România Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) compound is one of the most studied complex perovskite oxide with adequate properties for microwave applications, such as filters or antennas. BMT thin films were obtained by a modified sol-gel method, using the spin coating technique. Pt-coated Si or α-Al 2 O 3 plates were used as substrates. X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy and atomic force microscopy were employed for compositional, structural and morphological characterization of BMT samples. BMT thin films present single-phase compositions and cubic structure. The dielectric properties of BMT thin films were investigated at low frequency. Compusul Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) este unul dintre cei mai studiaţi oxizi perovskitici complecşi, cu proprietăţi adecvate pentru aplicaţii de microunde, de exemplu, filtre sau antene. Filmele subţiri BMT au fost obţinute printr-o metodă sol-gel modificată, utilizând tehnica “spin coating”. Ca substraturi au fost folosite plăcuţe de Si acoperit cu Pt sau de α-Al 2 O 3 . Pentru caracterizarea compoziţională, structurală şi morfologică a probelor BMT, s-a apelat la difracţie de raze X, spectroscopie de raze X cu dispersia energiei, microscopie electronică de baleiaj şi microscopie de forţă atomică. Filmele subţiri BMT prezintă fază unică şi structură cubică. Proprietăţile dielectrice ale filmelor subţiri BMT au fost investigate la frecvenţă joasă. Keywords: Sol-gel; Thin films; Dielectrics; Microwaves 1. Introduction With the recent revolution in mobile phone and satellite communication systems, using microwaves as carrier, the research and development in the field of components miniaturization has been one of the biggest challenges [1, 2]. The required properties in the case of high frequency dielectric materials are: high dielectric constant (ε r ), low dielectric loss (high quality factor - Q), thermal stability (small temperature coefficient of the resonant frequency - τ f , and of the permittivity - τ ε ) and good mechanical properties [1, 3]. Ba(Mg 1/3 Ta 2/3 )O 3 (BMT) compound is an important member of the A(B' 1/3 B" 2/3 )O 3 (A = Ba, Sr, Ca; B' = Mg, Zn, Ni, Co, Sr, Ca, Mn, Cd; B" = Nb, Ta) complex perovskites family and has a ε r of 25, a Q value of 36000 at 10 GHz and a temperature coefficient of resonant frequency of 4.4 ppm/°C [1]. Moreover, BMT presents a order - disorder phenomenon: when Mg and Ta cations are arranged in a random way over the B site, the crystal structure shows a disordered simple cubic symmetry, while the ordered compound adopts a 1:2 (Mg–Ta–Ta sequence) ordered hexagonal symmetry [4]. Many studies on the structure and electrical properties of BMT bulk ceramic revealed that the excellent microwave properties are given by the ordered structure [5]. The evolution of the ordered and disordered phases was described in terms of the nucleation and growth of small ordered domains with increasing annealing time and temperature [4, 6]. BMT bulk ceramic obtained by the conventional solid-state reaction method has been extensively studied owing to its potential applications in the electronics field. However, for achieving very good microwave dielectric properties, it requires high sintering temperatures (~ 1600 °C) and long annealing times (~ 100 h). Many investigations have been carried out regarding the use of sintering aids, dopants or glasses to reduce the sintering parameters without affecting the microwave dielectric properties [1, 5, 7, 8]. In order to overcome the disadvantages of the solid-state reaction method, soft chemistry techniques have been also used, but, in most cases, the researchers had to compromise on the microwave dielectric properties [9, 10]. In this context, growing thin films is a solution for both miniaturization and cost related problems. Thin films of dielectric materials offer the advantage of much lower crystallization temperatures, larger ∗ Autor corespondent/Corresponding author, Tel.: +4 0727 039 699, e-mail: cristinab@infim.ro