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.
Highlights
Colossal-permittivity (CP) materials (ε0 > 103 ) have potential uses in several technological applications, such as multilayer ceramic capacitors and memory devices [1]
All the observed diffraction peaks are consistent with the cubic structure according to JCPDS#75-2188, with no secondary phase peaks
Na1/2 La1/2 Cu3 Ti4 O12 ceramics were prepared by mechanochemical ball mill synthesis of the powder followed by spark plasma sintering (SPS) at 850–1025 ◦ C for 10 min under vacuum
Summary
Colossal-permittivity (CP) materials (ε0 > 103 ) have potential uses in several technological applications, such as multilayer ceramic capacitors and memory devices [1]. Intensive studies on CP materials during the last two decades have given rise to several material families with CP properties. The SSR method has the drawbacks of being a long, high-temperature process with less control on the resulting grain size of the ceramic. Compared to the standard SSR process, other methods aim to simplify the fabrication process and to reduce the maximum temperature and the time of the process without scarifying the dielectric properties of the ceramic. SPS is a comparatively new sintering technique that has the advantages of being fast due to the rapid heating rates and short dwelling times, which may lead to good control on the grain size of the resulting ceramics [17]
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