Abstract
(1−x)K0.5Na0.5NbO3−xBi(Zn2/3Nb1/3)O3 ((1−x)KNN−xBZN, x = 0.010, 0.015, 0.020, 0.025, and 0.030) lead-free ceramics were fabricated via a traditional solid-state method. The crystal structure, microstructure, dielectric, and conductivity behavior of this system were studied. Combined with X-ray diffraction (XRD) patterns, Rietveld refinement, and dielectric spectroscopy, an orthorhombic phase was determined for x = 0.010, an orthorhombic-tetragonal mixed phase was identified for x = 0.015, and a rhombohedral symmetry appears in 0.020 ⩽ x ⩽ 0.030. Both 0.98KNN−0.02BZN and 0.975KNN−0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent (tanδ) in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic. The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly, then drop sharply, and finally decline slowly, which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.
Highlights
Ceramic capacitors as essential electronic components have been largely applied in a variety of fields such as mobile communication, automotive electronics, and military devices [1,2]
Bi(Zn2/3Nb1/3)O3 (BZN) doped KNN ceramics exhibited high ε′ and low tan in a broad operational temperature region, which is highly favorable for the practical application of HTCC [22]
The crystal structure evolution and high-temperature conductivity behavior are both of fundamental interest for understanding dielectric properties of KNN-based materials [7,8]
Summary
Ceramic capacitors as essential electronic components have been largely applied in a variety of fields such as mobile communication, automotive electronics, and military devices [1,2]. Bi(Zn2/3Nb1/3)O3 (BZN) doped KNN ceramics exhibited high ε′ and low tan in a broad operational temperature region, which is highly favorable for the practical application of HTCC [22]. The crystal structure evolution and high-temperature conductivity behavior are both of fundamental interest for understanding dielectric properties of KNN-based materials [7,8]. A systematical study of crystal structure evolution is still lacking and the influence of BZN content on high-temperature conductivity behavior is unclear for this system. BZN modified KNN ceramics were fabricated to achieve the promising materials for HTCC application. To better understand dielectric properties of this system, the crystal structure evolution was determined by the X-ray diffraction (XRD) patterns, Rietveld refinement as well as dielectric spectroscopy, and the influence of BZN content on high-temperature conductivity behavior was revealed using the impedance spectroscopy. The ε', tan , and impedance data were collected by the means of an impedance meter (Agilent 4294A, USA) in a frequency range of 40 Hz−1 MHz from room temperature (RT) to 550 °C
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