Structural and dielectric properties of giant dielectric Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics prepared by reactive sintering methods

Abstract

Na0.5Sm0.5Cu3Ti4O12 (NSCTO) ceramics have been prepared by reactive sintering of amorphous powder. Spark plasma sintering (SPS) for 10 min at 1025 °C and conventional sintering (CS) for 10 h at 1090 °C have been employed. X-ray diffraction measurements confirmed the pure CCTO-like phase for SPS and CS NSCTO ceramics. The SPS ceramic showed an average grain size of 500 nm, which is much smaller than that of the CS ( ∼ 5 μ m ) sample. The impedance spectroscopy measurements revealed an electrically inhomogeneous structure in the prepared ceramics. While the resistivities of grains of both ceramic samples were in the same order of magnitude, the resistivity of grain-boundaries of the CS ceramic was three orders of magnitude greater than that of the SPS ceramic. Both of the samples showed giant dielectric constant ( > 10 3 ) over wide ranges of temperatures and frequencies. Nevertheless, the room-temperature dielectric loss of the SPS NSCTO (3.2 at 1.1 kHz) ceramic sample was higher than that of the CS NSCTO (0.08 at 1.1 kHz) ceramic sample due to the reduced grain-boundary resistivity of the former. Two dielectric relaxations were detected for each sample and attributed to the relaxations in grains and grain-boundaries. The dielectric behavior of the SPS and CS NSCTO ceramics could be interpreted in terms of the internal barrier layer capacitor (IBLC) model.

Sintering Temperature, Frequency, and Temperature Dependent Dielectric Properties of Na0.5Sm0.5Cu3Ti4O12 Ceramics

“…By using the best-fit method (UnitCellWin software [17]), the lattice parameter was calculated from hkl and 2θ values of the XRD peaks. The lattice parameter for the current ceramics was found to be in the following range 7.391-7.395 Å, which agrees with the reported value of 7.394 Å for NSCTO ceramics [3,15].…”

“…Both Materials 2021, 14, 4805 2 of 13 conventional sintering (CS) inside a tubular furnace in air (10 h at 1090 • C) and spark plasma sintering (SPS) (10 min at 1025 • C) under vacuum were studied. The reactively sintered NSCTO ceramics showed giant relative permittivity (ε > 10 3 ) but high dielectric loss (tanδ > 0.08) at 1.1 kHz and 300 K [15]. In the current investigation, 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.…”

“…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. These studies include the doping of CCTO to control the electrical properties of grain and grain-boundary of the ceramic [10][11][12][13][14], using simplified processes such as reactive sintering and sol-gel synthesis [12,15], and/or using of novel sintering techniques such as microwave sintering [4] and spark plasma sintering [6,13]. Na 0.5 Sm 0.5 Cu 3 Ti 4 O 12 (NSCTO) ceramics showed interesting properties in terms of colossal relative permittivity (10 3 -10 5 ) [16].…”

“…Na 0.5 Sm 0.5 Cu 3 Ti 4 O 12 (NSCTO) ceramics showed interesting properties in terms of colossal relative permittivity (10 3 -10 5 ) [16]. Recently, 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 then directly sintered without passing by a calcination step.…”

Improved dielectric properties of Na1/2Y1/2Cu3Ti4O12 ceramics synthesized by ball-milling and reactive sintering

“…According to this model, the apparent giant dielectric constant arises due to the Maxwell-Wagner polarization effects at internal resistive boundaries such as grain-boundaries and/or domain-boundaries. Recently, a great deal of studies on the effects of doping, powder synthesis and sintering techniques on the dielectric properties of CCTO has been carried out [2][3][4][10][11][12][13][14][15][16]. Most of these studies used the solid state reaction (SSR) technique for the fabrication of ceramics.…”