Effect of minor phase (CuO) on sinterability, grain size, and dielectric properties of CaCu 3 Ti 4 O 12 ceramics
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Effect of minor phase (CuO) on sinterability, grain size, and dielectric properties of CaCu3Ti4O12 ceramics Taranveer Kaur1 · Shivani Punj1 · Ravindra Kumar2 · Kulvir Singh1 Received: 2 June 2020 / Accepted: 31 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract CaCu3Ti4O12 (CCTO) electro ceramic was prepared by a solid-state reaction technique. The formation of CCTO was confirmed by X-ray diffraction (XRD). Pellets of calcined powder were sintered at different temperatures for two different durations, i.e., 2 and 10 h (h). The morphology and grain size of the samples were observed using scanning electron microscopy (SEM). SEM images showed that the minor phase (CuO) plays an important role in the growth of grain size. It seems that higher sintering temperatures led to change in the oxidation states of Cu and Ti, which increase the volume fraction of the CuO minor phase. Dielectric studies show that the dielectric constant is increasing with increasing sintering temperature, holding time, and presence of the CuO phase. The highest dielectric constant of ~ 41,000 was observed for CCTO samples sintered at 1100 °C for 10 h. The present samples find application in the energy storage devices. Keywords CaCu3Ti4O12 · X-ray diffraction · Grain size · Microstructure · Dielectric properties
1 Introduction There has been considerable interest in the study of the giant dielectric permittivity of the cubic A BO3 perovskite-type materials, which could help in the miniaturization of the electronic components. Additionally, it could also find applications in charge storage devices like supercapacitors that have lots of applications in automobiles, electrical industries, etc. [1, 2]. The CaCu3Ti4O12 compound (CCTO) has recently attracted much interest due to its extraordinarily high static dielectric constant up to 1 05 and possesses good temperature stability over a wide range of temperatures between 100 and 400 K [3, 4]. Subramanian et al. [5] first reported the high dielectric constant at 1 kHz in A Cu3Ti4O12 and ACu3Ti3FeO12 phases (A = trivalent rare earth or Bi). Barbier et al. [6] had reported high values of the dielectric permittivity (εr ~ 1.4 × 105) and relatively small dielectric losses (tan δ ∼ 0.16) at 1 kHz and room temperature for CCTO-based ceramics. Although there are many theories * Kulvir Singh [email protected] 1
School of Physics and Materials Science, Thapar Institute of Engineering and Technology, Patiala, Punjab 147004, India
IIMT Group of Colleges, Noida, Uttar Pradesh, India
2
that explain the high dielectric constant of the CCTO, none can explain its origin efficiently and convincingly. At present, the most accepted theory is of internal barrier layer capacitance, which suggests that this high value of dielectric may be due to planar defects or domain boundaries in these non-centrosymmetric materials [7–9]. There are many studies regarding the effect of various structural and processing parameters, such as synthesis technique, sample thickness, sintering
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