Processing influence in the CaCu 3 Ti 4 O 12 electrical properties
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Processing influence in the CaCu3Ti4O12 electrical properties Lucas Lion Kozlinskei1 · Alisson T. de Andrade Paes2 · Edson Cezar Grzebielucka1 · Christiane Philippini F. Borges1 · André Vitor Chaves de Andrade3 · Eder Carlos F. de Souza1 · Sandra Regina M. Antunes1 Received: 8 April 2020 / Accepted: 13 May 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract CaCu3Ti4O12 (CCTO) is a complex oxide with a perovskite structure that is widely studied due to its dielectric and nonohmic properties. The formation and composition of grains and grain boundaries are very important factors to improve these electrical properties. In this work, CCTO-based ceramics were processed by solid-state reaction at different calcination temperatures (700 °C to 1000 °C, for 4 h) and sintering at 1100 °C for 6 h aiming optimization in capacitor–varistor properties. The changes in crystal phase composition observed via XRD and chemical contrasts visualized by SEM/EDS point out that the disappearance of the secondary CuO phase of calcined powders is linked to complete Cu ion incorporation to the crystal structure of CCTO. This phenomenon culminated in sinterization via liquid phase formation, with abnormal grain growth for samples calcined at temperatures higher than 900 °C. The calcination occurring at 800 °C for 4 h, to produce CCTO with a more homogeneous microstructure, with apparent porosity of 2.67%, α of 5.49, EB of 1505 V cm−1, ε′ (1 kHz) of 7506 and ΦB of 0.754 eV, was considered the best processing condition. Keywords CCTO · Processing · Impedance · Varistor · Dielectric constant · Non-ohmic properties
1 Introduction CaCu3Ti4O12 (CCTO) is a complex oxide with a perovskite type structure belonging to the titanate family. This compound is extensively studied in the field of materials since the discovery of its colossal dielectric constant (104–105) [1]. Since then, several studies were carried out to improve its dielectric properties from adjustments in processing parameters [2–8] or by doping [9–18]. In the last decade, many studies on the non-ohmicity of CCTO-based systems began to emerge [19–28], where some authors reported the technological potential of this material not only as a capacitor, but also as a varistor. * Edson Cezar Grzebielucka [email protected] 1
Programa Pós‑Graduação em Química Aplicada, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84.030‑900, Ponta Grossa, Paraná, Brazil
2
Departamento de Química, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84.030‑900, Ponta Grossa, Paraná, Brazil
3
Programa de Pós‑Graduação em Ciências/Física, Universidade Estadual de Ponta Grossa, Av. Gen. Carlos Cavalcanti 4748, 84.030‑900, Ponta Grossa, Paraná, Brazil
The difficulties in terms of the actual application of this material as a capacitor or varistor are mainly due to the need to optimize some properties, such as the decrease in tan δ and increase in nonlinear coefficient α, and in its preparation, since the high oven times at high t
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