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Dielectric Properties of Colossal-Dielectric-Constant Na1/2La1/2Cu3Ti4O12 Ceramics Prepared by Spark Plasma Sintering
Authors:Hicham Mahfoz Kotb  Mohamad Mahmoud Ahmad  Sajid Ali Ansari  Tarek S Kayed  Adil Alshoaibi
Institution:1.Department of Physics, College of Science, King Faisal University, Al-Hassa 31982, Saudi Arabia; (M.M.A.); (S.A.A.); (A.A.);2.Department of Physics, Faculty of Science, Assiut University, Assiut 71516, Egypt;3.Department of Physics, Faculty of Science, The New Valley University, El-Kharga 72511, Egypt;4.Department of Basic Engineering Sciences, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 34221, Saudi Arabia;
Abstract:In the current study, we report on the dielectric behavior of colossal-dielectric-constant Na1/2La1/2Cu3Ti4O12 (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma sintering (SPS) at 850 °C, 900 °C, and 925 °C for 10 min. X-ray powder diffraction analysis showed that all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS NLCTO ceramics showed a room-temperature colossal dielectric constant (>103) and a comparatively high dielectric loss (>0.1) over most of the studied frequency range (1 Hz–40 MHz). Two relaxation peaks were observed in the spectra of the electrical modulus and attributed to the response of grain and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance (IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary of SPS NLCTO.
Keywords:colossal dielectric constant  spark plasma sintering (SPS)  NLCTO  CCTO
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