A High‐Temperature‐Capacitor Dielectric Based on K_0.5Na_0.5NbO₃‐Modified Bi_1/2Na_1/2TiO₃–Bi_1/2K_1/2TiO₃

Abstract

A high‐temperature dielectric, (1–x)(0.6Bi1/2Na1/2TiO3–0.4Bi1/2K1/2TiO3)–xK0.5Na0.5NbO3, off the morphotropic phase boundary of the parent matrix 0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3, has been developed for application as a high‐temperature capacitor. In addition to temperature‐dependent permittivity and dielectric loss, DC conductivity and field‐dependent permittivity are reported. These properties are correlated with temperature‐dependent structure data measured at different length scales using Raman spectroscopy and neutron diffraction. It is suggested that all materials investigated are ergodic relaxors with two types of polar nanoregions providing different relaxation mechanisms. The most attractive properties for application as high‐temperature dielectrics are obtained in a material with x = 0.15 at less than 10% variation of relative permittivity of about 2100 between 54°C and 400°C.

High-temperature dielectrics in CaZrO3-modified Bi1/2Na1/2TiO3-based lead-free ceramics

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Among them, the ceramic-based ferroelectric materials are the most promising due to their inherently good temperature stability and dielectric properties. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] As a consequence of new regulations that restrict the use of toxic elements in consumer products, 26 considerable efforts have been made in the last years to produce nontoxic lead-free ferroelectric materials with suitable dielectric properties. 14-25 A number of studies focused on the development of BT-based dielectrics and piezoelectric materials functioning over a wide temperature range.…”

Local structure change evidenced by temperature-dependent elastic measurements: Case study on Bi1/2Na1/2TiO3-based lead-free relaxor piezoceramics

“…For example, incorporation of K 0.5 Na 0.5 NbO 3 (KNN), 8 SrTiO 3 (ST), 9 BiAlO 3 (BA), 10 or BiZn 1/2 Ti 1/2 O 3 (BZT) 11 allows for large field-induced strains, the origin of which was recently identified as incipient piezoelectricity, 12,13 or nearly temperature-insensitive permittivity for high-temperature capacitors. 14 The crystal structure and its thermal evolution are still under debate for many BNT-based systems. 3,15 Hightemperature diffraction studies have so far not provided a conclusive explanation for the features observed in the hightemperature permittivity measurements possibly due to the inherent resolution limit of the diffraction techniques.…”

Enhancement of energy-storage properties of K0.5Na0.5NbO3 modified Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 lead-free ceramics

“…It could be seen that the maximum permittivity peak was significantly lowered with increasing KNN from the e r -T curves. That might be caused by the incorporation of KNN [22]. The interval between the adjacent oxygen octahedral was shrunk by the A-site vacancies.…”