Effect of Nb 2 O 5 substitution on the dielectric characteristics of DyTiTaO 6 microwave ceramics James T. Joseph a , H. Padma Kumar b , M.R. Varma b,c , J.K. Thomas d , Sam Solomon b, ⁎ a Department of Chemistry, St. John's College, Anchal 691 306, Kerala, India b Department of Physics, St. John's College, Anchal 691 306, Kerala, India c National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram, Kerala, Pin-695019, India d Department of Physics, Mar Ivanios College, Thiruvananthapuram, 695 015, Kerala, India Received 14 May 2007; accepted 25 July 2007 Available online 31 July 2007 Abstract Ceramic materials of the type DyTiNb x Ta 1 - x O 6 were prepared by conventional solid-state route for different values of x. The materials were characterized by X-ray diffraction and Scanning Electron Microscopy. Dysprosium titanium niobate has a negative τ f with euxenite orthorhombic structure while dysprosium titanium tantalate has a positive τ f with aeschynite orthorhombic structure. The dielectric properties in the microwave frequency region were measured. A small amount of Nb substitution for Ta produced a large change in microwave dielectric properties. The τ f and ɛ r decrease with the increase in concentration of niobium. All the samples have high quality factor and hence suitable for microwave applications. © 2007 Elsevier B.V. All rights reserved. Keywords: Ceramics; Electronic materials; Sintering; Dielectric properties 1. Introduction Recent progress in wireless communication resulted in an increased demand for new materials suitable for microwave applications. Ceramic Dielectric Resonators (DRs) have the advantage of more miniaturization and high quality factor than other techniques like transmission lines, micro strips and cavities. Widespread research is going on in the field of Dielectric Resonators (DRs) as they have high dielectric constant, high quality factor and small variation of resonant frequency with respect to temperature [1–9]. Rather, their cost of production is low in comparison with other high frequency devices and is characterized by light weight and compactness. It is interesting to note that most of the DRs with good dielectric properties are complex oxides of titanium, niobium and tantalum. It was reported by Komkov and later by Qi et al. that RETiNbO 6 compounds belong to the above family with lanthanide of atomic numbers in the range of 57–63 have orthorhombic aeschynite structure and those in the range of 64–71 have orthorhombic euxenite structure [10,11]. In 1974 Kazantsev et al. have shown that rare earth titanium tantalate compounds with rare earths of atomic numbers in the range of 57–66 have orthorhombic aeschynite symmetry, while those in the range of 67–71 have orthorhombic euxenite symmetry [12]. Sebastian et al. have reported the microwave dielectric properties of RETiNbO 6 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y and Yb) ceramics [13]. They observed that aeschynite RETiNbO 6 materials have positive τ f with high dielectric constant while euxenite compounds have negative τ f with a lower dielectric constant. Surendran et al. have reported a similar observation in the case of RETiTaO 6 ceramics also [14]. Hence it is possible to get a series of DRs with their τ f ranging from negative to positive and dielectric constant from low to high, by preparing ceramics of the type DyTiNb x Ta 1 - x O 6 . In this paper we report the synthesis, characterization and microwave dielectric properties of DyTiNb x Ta 1 - x O 6 dielectric resonators. 2. Experimental DyTiNb x Ta 1 - x O 6 ceramic samples were prepared by conventional solid-state ceramic route for varying values of x Available online at www.sciencedirect.com Materials Letters 62 (2008) 1064 – 1066 www.elsevier.com/locate/matlet ⁎ Corresponding author. Tel.: +91 09847314237; fax: +91 471 2532445. E-mail address: samdmrl@yahoo.com (S. Solomon). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.07.045