High temperature dielectric ceramics: a review of temperature-stable high-permittivity perovskites

Abstract

Recent developments are reviewed in the search for dielectric ceramics which can operate at temperatures > 200ºC, well above the limit of existing high volumetric efficiency capacitor materials. Compositional systems based on lead-free relaxor dielectrics with mixed cation site occupancy on the perovskite lattice are summarised, and properties compared. As a consequence of increased dielectric peak broadening and shifts to peak temperatures, properties can be engineered such that a plateau in relative permittivity-temperature response ( r-T) is obtained, giving a ±15%, or better, consistency in r over a wide temperature range. Materials with extended upper temperature limits of 300°C, 400°C and indeed 500°C are grouped in this article according to the parent component of the solid solution, for example BaTiO3 and Na0.5Bi0.5TiO3. Challenges are highlighted in achieving a lower working temperature of -55°C, whilst also extending the upper temperature limit of stable r to ≥ 300°C, and achieving high-permittivity and low values of dielectric loss tangent, tan . Summary tables and diagrams are used to help compare values of r, tan , and temperature ranges of stability for different materials.

Current Understanding of Structure–Processing–Property Relationships in BaTiO3–Bi(M)O3 Dielectrics

“…In the continual quest for increased integration, efficiency, and process monitoring, electronics systems are being subjected to increasingly harsh operating conditions. One key class of components that has received a great deal of attention over the past decade is capacitors that can operate efficiently and reliably under large fields and at temperatures ≥200°C . For example, devices built around wide bandgap semiconductors such as SiC and GaN can operate with greater efficiency, higher frequencies, and higher powers than their Si‐based counterparts, but even these more efficient devices dissipate sufficient heat that active cooling is often required in order to accommodate the operating temperature limitations of nearby passive components such as capacitors.…”

Ferroelectric to Relaxor Transition in BaTiO3–Bi(Zn2/3Nb1/3)O3 Ceramics

“…Driven by the restriction legislation of lead contamination and the demand of high‐temperature (>200°C) applications in such as oil drilling, defense, aerospace, and automotive under‐the‐hood, a range of lead‐free bismuth‐based ceramics, especially the BaTiO 3 –BiMeO 3 (Me symbolizes the trivalent or averagely trivalent metallic cations) ceramics, have been under intensive exploration . Most of these materials are relaxor dielectrics with frequency‐dependent permittivity peaks, showing excellent temperature stability.…”

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

“…The main drawback of BT is the sharp Curie point near ~126°C which hinders its use in higher temperature applications . A number of material systems have been proposed in the past for high‐temperature applications; among which, BaTiO 3 ‐BiMg 0.5 Ti 0.5 O 3 (BT‐BMT) has attracted a considerable attention because of its high relative permittivity . The defect chemistry of both end‐members (BT and BMT) show that the electrical conductivity is dominated by oxygen ion conduction.…”