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D6.7.1

Structural and dielectric properties of Ca1-x MgxCu3Ti4O12 thin films L. A. Bermúdez, R. P. Guzman, M.S.Tomar, R.E. Melgarejo, Physics Department, University of Puerto Rico, Mayagüez, PR 00681-9016 ABSTRACT Ca1-xMgxCu3Ti4O12 material has been synthesized by chemical route for different compositions and thin films have been deposited by spin coating. X-ray diffraction and Raman spectroscopy were used for detailed characterization of this material for both powder and thin films. X-ray diffraction shows single phase film material for different compositions x < 0.80. The initial measurements on dielectric response indicates high dielectric constant > 10, 000 for the composition x = 0.1. INTRODUCTION Perovskite like ACu3Ti4O12 family of materials [1] where A is divalent cations, are of great interest for their dielectric application. The complex perovskite compounds CaCu3Ti4O12 (CCTO) has attracted considerable attention due to its high dielectric response at lower frequencies [2, 3] and nearly constant over a wide temperature range (100 - 600 K). In addition, the study [4] also shows that above the frequency range between 102 Hz and 106 Hz, the dielectric constant drops to about 100. Large dipole moments in some perovskite like materials are due to ionic displacements within the centro-symmetric structures, but Raman scattering studies [4] of CCTO indicates no structural phase transition between 20 and 600 K. If Ca ion is replaced by divalent ion such as Mg, Sr, Ba, Cd, the dielectric and structural behavior may change. We report here for the first time the synthesis and structural properties of Ca1xMgxCu3Ti4O12

thin films prepared by sol-gel process for various compositions and its dielectric

response for the composition x = 0.1.

EXPERIMENTAL RESULTS AND DISCUSSION For the synthesis of Ca1-xMgxCu3Ti4O12, acetate/nitrate of Ca, Mg, and Cu and titanium isopropoxide for Ti were used as precursors. The appropriate amount of the salts were mixed individually in solvent such as methoxy-ethanol and acetic acid and mixed hot to make stoichiometric solution. Both powder and films were prepared by proper sol-gel process. Thin films were deposited on Pt substrate (Pt/TiO2/SiO2/Si) by spin coating at 3000 rms. The post

D6.7.2

annealed films were annealed at 750o C for an hour, and the powder samples at the at 900o C for four hours.

Structural properties on films and powder samples were studied using x-ray

diffraction and Raman spectroscopy, and the dielectric response was measured on the film with composition x = 0.1. Cu Kα radiation (0.15495 nm) was used for recording x-ray diffraction patterns on Mg substituted CaCu3Ti4O12 materials using Siemens D5000 x-ray diffractometer. Figure 1 shows the x-ray diffraction patterns on powder samples for the compositions: x = 0.0, 0.2, 0.3, 0.4, 0.6, 0.7, 0.8, 0.9, and 1.0. For comparison, the x-ray patterns on thin films deposited on Pt substrate (Pt/TiO2/SiO2/Si) by sol-gel process for x = 0.0, 0.2, 0.3, 0.4, and 0.6 is shown in Fig. 2. It is observed that it makes a solid s