Abstract
NSCTO (Na0.5Sm0.5Cu3Ti4O12) ceramics have been prepared by reactive sintering solid-state reaction where the powder was prepared from the elemental oxides by mechanochemical milling followed by conventional sintering in the temperature range 1000–1100 °C. The influence of sintering temperature on the structural and dielectric properties was thoroughly studied. X-ray diffraction analysis (XRD) revealed the formation of the cubic NSCTO phase. By using the Williamson–Hall approach, the crystallite size and lattice strain were calculated. Scanning electron microscope (SEM) observations revealed that the grain size of NSCTO ceramics is slightly dependent on the sintering temperature where the average grain size increased from 1.91 ± 0.36 μm to 2.58 ± 0.89 μm with increasing sintering temperature from 1000 °C to 1100 °C. The ceramic sample sintered at 1025 °C showed the best compromise between colossal relative permittivity (ε′ = 1.34 × 103) and low dielectric loss (tanδ = 0.043) values at 1.1 kHz and 300 K. The calculated activation energy for relaxation and conduction of NSCTO highlighted the important role of single and double ionized oxygen vacancies in these processes.
Highlights
We report on the effect of the temperature of reactive conventional sintering (CS) inside a tubular furnace in air on the dielectric and structural properties of Na0.5 Sm0.5 Cu3 Ti4 O12 (NSCTO) ceramics
These patterns confirm the formation of CCTO-like cubic phase (JCPDS card no. 75-2188)
By using the best-fit method (UnitCellWin software [17]), the lattice parameter was calculated from hkl and 2θ values of the X-ray diffraction (XRD) peaks
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Studies aiming at simplifying the fabrication process and reducing the dielectric loss at enough low level (tanδ < 0.05) while maintaining the colossal permittivity of titanate-based ceramics are still ongoing. We reported on the dielectric properties of NSCTO prepared by reactive sintering solid-state reaction [15] In this method, the starting raw materials are milled for several hours directly sintered without passing by a calcination step. The reactively sintered NSCTO ceramics showed giant relative permittivity (ε0 > 103 ) but high dielectric loss (tanδ > 0.08) at 1.1 kHz and 300 K [15]. We report on the effect of the temperature of reactive CS inside a tubular furnace in air on the dielectric and structural properties of NSCTO ceramics. The dielectric spectra of the ceramics have been investigated in broad temperature and frequency ranges
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