Abstract
In this paper, we examined the dielectric properties of CaCu3Ti4O12 (CCTO) ceramics fabricated by various routes and discussed the most important conditions affecting their dielectric behavior. We prepared feedstock powder using a molten salt route and compared it with a commercial powder. Both powders were sintered using SPS. For some samples, annealing was applied after sintering. Other samples were obtained by high-pressure forming and conventional sintering, using both powders. Phase composition, porosity and microhardness were evaluated in comparison with the literature. The results showed that a sintering temperature just below or equal to 1000 °C should be set for the SPS process. However, the best dielectric characteristics were obtained in samples prepared by high-pressure forming and conventional sintering, which showed a relative permittivity of 22,000 and a loss tangent of 0.13 at 1 MHz.
Highlights
Ceramic capacitors represent one of the basic electronic components
Because of the repeated presence of carbon in the Spark plasma sintering (SPS) samples and of the strong chemically reducing conditions during SPS, we focused on the development of alternative processing routes to produce high-quality CCTO dielectrics by applying the lowest possible thermal load
The molten salt synthesis process was successful in obtaining powder P1 with a CCTO percentage of over 80%, but with the presence of CaTiO3, TiO2 and CuO as secondary phases and small residues of NaCl
Summary
While some materials show appropriate properties, scientists still examine new materials, or new combinations of existing ones, in order to obtain improved electrical properties Some examples of such materials are represented by doped-BaTiO3, doped-TiO2, CaCrTi2O6 and CaCu3Ti4O12, which show comparatively high, so-called giant, values of relative permittivity (εr = 104 or higher) [1,2]. The IBLC could be further divided into macroscale barrier layer capacitance (MBLC) and nanoscale barrier layer capacitance (NBLC) [9] It is reported, that the high dielectric constant might be related to the high electrical conductivity [5], which is mediated by oxidation. The grain boundaries oxidize faster than the bulk of the grain, lowering their electrical conductivity compared to that of the bulk grains
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