New Lead Free Perovskites with a Diffuse Phase Transition: NaNbO3 Solid Solutions

Novel High‐Temperature Antiferroelectric‐Based Dielectric NaNbO3–NaTaO3 Solid Solutions Processed in Low Oxygen Partial Pressures

“…In addition, these solid solutions also showed a thermal hysteresis behavior over a broad temperature range. These observations are consistent with previous reports in air‐fired NaNbO 3 –NaTaO 3 solid‐state system; therefore, we infer that low p O 2 firing does not strongly affect the phase transition behavior in this system similar to (Na 0.5 K 0.5 )NbO 3 ceramic . Although the temperature coefficient of dielectric constant was relatively large and this system should be modified compositionally to satisfy, for example, Class I (temperature change is less than 30 ppm/ o C) and X8R specifications, the high dielectric constant and low dielectric loss above 200°C are attractive and provide a promising solution for high‐temperature dielectrics.…”

“…Therefore, the superlattice reflections observed in the reduced fired NTN ceramic are consistent with a core region with an inhomogeneous structure somewhere between AFE Pbcm and ferroelectric Pbnm phases. It is well‐known that the Li substitution into A‐site induces a ferroelectric phase in NaNbO 3 . Furthermore, Kahn et al .…”

“…This is interesting, both from scientific and practical viewpoint, because it implies that the ceramics which have both AFE and ferroelectric characteristics can be developed by using NaNbO 3 –NaTaO 3 solid‐state system. Recently, Raevski and Prosandeev studied the relaxor behavior in NaNbO 3 –NaTaO 3 ceramic and showed that this has high permittivity and small temperature coefficient of capacitance (TCC) owing to a diffused transition. Earlier studies with PbZrO 3 points to the advantage of using compositional designs that create a diffuse and incommensurate phase transition, with irrational superlattice reflections .…”

“…Therefore, this system is considered to be a promising candidate for high‐temperature capacitor application with base metal inner electrode. Many studies have been reported on this system; however, all of them focused on the air‐fired ceramics, and there are no reports about the properties and microstructure of low p O 2 fired NaNbO 3 –NaTaO 3 ceramics. The objective of this study is to demonstrate a new research and technological path for high‐temperature dielectrics using AFE‐like phases based on alkali‐niobate perovskite materials.…”

Landau theoretical analyses of phase transitions and ferroelec-tricity in antiferroelectric ferroics

“…It was reported that for some groups of AFE perovskites, the values are lower than values [22]. Rearrangement of equation 21 results to:…”