Evaluation of the effect of the stoichiometric ratio of Ca/Cu on the electrical and microstructural properties of the CaCu₃Ti₄O₁₂polycrystalline system

Abstract

The structural, microstructural, non-ohmic and dielectric properties of perovskite-type CaCu3Ti4O12 (CCTO) with Ca/Cu stoichiometries of 1/3, 1/1 and 3/1 are discussed. The 1/3 Ca/Cu ratio system presents very high dielectric permittivity (∼9000 at 10 kHz) and a low non-ohmic property (α = 9), whereas the 1/1 Ca/Cu ratio system shows the opposite effect, i.e. the dielectric permittivity decreases (2740 at 10 kHz) and the non-ohmic property increases (α = 42), indicating that these properties are not directly correlated. The results of this work reinforce the idea that the greatest contribution to the very high permittivity is caused by the presence of planar defects inside the CCTO grains, generating internal nanometric domains associated with stacking faults, according to the nanoscale barrier layer capacitance model proposed very recently in the literature [1]. The non-ohmic property is related to the presence and distribution of phases such as CaTiO3 (CTO) and CuO, segregated or precipitated at the grain boundary, which generate large numbers of electrically active interfaces.

Improved dielectric and non-ohmic properties of Ca2Cu2Ti4O12 ceramics prepared by a polymer pyrolysis method

“…Additionally, a small amount of CuO phase can be observed in the XRD patterns of the SSR-ceramics, corresponding to the result observed in the TEM micrograph of the CCTO/CTO ceramic reported in Ref. [17]. Considering the nominal composition of Ca 2 Cu 2 Ti 4 O 12 , the formation of the CCTO/CTO composite consisting of ∼33.3 mol% of CCTO and ∼66.7 mol% of CTO is caused by the imbalance between the Ca and Cu atoms [15].…”

“…Accordingly, the two most important parameters related to the non-ohmic properties, i.e., non-linear coefficient (˛) and breakdown field (E b ), of the CCTO/CTO ceramics are calculated from these curves.˛calculated in the range of 1-10 mA/cm 2 of the SSR-5, SSR-10, PP-5, and PP-10 samples are found to be 6.48, 11.36, 10.87, and 10.59, respectively. These values are much lower than the values of 42-65 as reported in the literatures [15][16][17]. The E b values of the samples obtained at J = 1 mA/cm 2 are 5953, 10385, 12083, and 10616 V/cm, respectively.…”

“…The ceramics were polished and electroded by silver paint on both sides of the disk-shape samples. The dielectric response of the samples was measured using an Agilent E4980A Precision LCR Meter over the frequency and temperature ranges of [14][15][16][17]. Additionally, a small amount of CuO phase can be observed in the XRD patterns of the SSR-ceramics, corresponding to the result observed in the TEM micrograph of the CCTO/CTO ceramic reported in Ref.…”

“…Considering the nominal composition of Ca 2 Cu 2 Ti 4 O 12 and compared to the CaCu 3 Ti 4 O 12 composition, this ceramic consists of ∼33.3 mol% of CCTO and ∼66.7 mol% of CaTiO 3 (CTO), resulting from the imbalance between the Ca and Cu atoms [15]. Besides such improved dielectric properties, it was revealed that the CCTO/CTO composite ceramics also exhibited high non-linear coefficient values (˛∼42-65) with high breakdown field extracted from the J-E curves [16,17]. Furthermore, the sintering temperature of the CCTO/CTO ceramic composites (∼1050-1100 • C) is much lower than that of BaTiO 3 (∼1350 • C), which is the ferroelectric ceramic that can exhibit the high ε and low tan ı values of about 2000 and 0.02, respectively [14].…”

Polyarylene Ether Nitrile-Based High-k Composites for Dielectric Applications

“…In comparison, the dielectric constant of ferroelectric ceramics can be as high as 10 4 with extremely low dielectric loss and excellent thermal stability, which meets the requirements of most application devices [16,17]. These ferroelectric ceramic dielectrics exhibiting relatively higher permittivity have attracted tremendous research enthusiasm because of their applications as power transmission system, high-energy storage capacitor, microwave communication, and so on [18][19][20]. However, to fulfil demands from the electronic industry, it is still a challenge with critical importance to fabricate lightweight and portable equipment with these inorganic dielectric materials.…”