Effects of TiO 2 Addition on the Radio-Frequency Properties of the Sr 2 CoNbO 6 Matrix J.E.V. DE MORAIS, 1 R.G.M. OLIVEIRA , 1,6 V.L. BESSA, 1,3 D.B. FREITAS, 1,3 J.C. SALES, 1 F.F. DO CARMO, 1,4 D.X. GOUVEIA, 1,5 M.A.S. SILVA, 1 and A.S.B. SOMBRA 1,2 1.—Physics Department, Telecommunication, Materials Science and Engineering of Laboratory (LOCEM), P.O. Box 6030, Fortaleza, Ceara ´ 60455-760, Brazil. 2.—Federal University of Semiarid Region, UFERSA, Mossoro, RN 59625-900, Brazil. 3.—Telecommunication Engineering Department, Federal University of Ceara ´ (UFC), Fortaleza, Brazil. 4.—Chemistry Department, Federal University of Ceara ´ (UFC), Fortaleza, Brazil. 5.—Federal Institute of Ceara ´, Campus Fortaleza/IFCE, Fortaleza, Ceara ´ 63400-000, Brazil. 6.—e-mail: ronaldomaia@fisica.ufc.br In this work, the investigation of Sr 2 CoNbO 6 –TiO 2 composite, which shows interesting dielectric characteristics (low loss and high dielectric permittivity), was carried out. The Sr 2 CoNbO 6 (SCNO) system is widely applied in electro- electronic devices due to their dielectric characteristics. SCNO was synthe- sised via solid state reaction, and x-ray diffraction was used for structural characterisation. Impedance spectroscopy was used to characterise the material in the radiofrequency range where the real impedance of the SCNO showed high values, and the imaginary impedance showed a relaxation time. The thermo active process was studied by the Arrhenius equation in the SCNO–TiO 2 composite series, which showed a considerable increase in acti- vation energy. Nyquist diagrams showed the presence of a semicircle that was fitted using a model of the equivalent R-CPE circuit, showing a similar profile in all studied samples. Key words: SCNO, dielectric properties, radiofrequency, DRA INTRODUCTION The search for new materials with electrical properties that may be useful for some engineering fields has grown considerably in recent years. The advancement of mobile communications and satel- lite communications systems using microwaves and radio-frequency a carrier has generated a great demand for dielectric resonators, 1 as well as in the field of the development of high performance elec- tronic materials and high frequency circuits, with a low cost of manufacture, where several families of ceramic materials are used. 2 The high interest in ceramic materials in the field of telecommunications is due to their properties in the range of radiofrequency, microwaves and millimeter waves. Generally, ceramics have higher dielectric permittivity and low loss as compared to metallic materials. In this way, several devices can be miniaturised using dielectric resonators (DR) with these dielectric properties. 1,3 These ceramic materials, as well as metal oxides, can be classified according to their structure or chemical character- istics, such as spinel and perovskite. The structural formula of the perovskite is composed of ABX 3 , where A is a large cation closed in layers with oxygen ions and B is a small metal ion located in the octahedral coordinates. Many perovskites have dif- ferent symmetry from the cubic at room tempera- ture (hettotype), but at high temperatures (aristotype) they exhibit cubic symmetry and in some cases tetragonal. In addition to the structure ABO 3 to define an oxide as a perovskite structure, it must satisfy the ratio of ionic rays provided in Eq. 1, called the Goldsmith tolerance factor (t): 4,5 (Received September 21, 2019; accepted December 18, 2019) Journal of ELECTRONIC MATERIALS https://doi.org/10.1007/s11664-019-07918-9 Ó 2020 The Minerals, Metals & Materials Society