Effect of the (Ba + Sr)/Ti ratio on the microwave-tunable properties of Ba0.6Sr0.4TiO3 ceramics

Takasi Teranisi, Riku Kanemoto, Hidetaka Hayashi, Akira Kishimoto

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The impact of the (Ba + Sr)/Ti (A/B) ratio on the microwave-tunable characteristics of diffuse phase transition (DPT) ferroelectric Ba0.6Sr0.4TiO3 (0.6-BST) ceramics was investigated. The reduction in the lattice constant with increasing nonstoichiometry was attributed to introduced partial Schottky defects, i.e., (Formula presented.) and (Formula presented.). The magnitude of the dielectric constant, ε′, at room temperature in the absence of an applied electric field was governed by the shift in the dielectric maximum temperature, Tm, because Tm was close to room temperature for the 0.6-BST. The dielectric loss, tanδ, diminished as the ε′ decreased for 0.98≤A/B≤1.05, while the tanδ was much higher for A/B=0.95 having the greatest A-site vacancy loading. The negatively charged VˮBa and Vˮsr were mainly compensated by oxygen vacancies and likely partly compensated by holes, h, which contributed to the electrical conduction. The tunability, T, at 100 MHz was almost constant at 20%–25% for A/B≥1.00 despite the reduction of the ε′, whereas T decreased for A/B<1.00 to ca. 10% for A/B=0.95 having the greatest A-site vacancy loading. The results implied that the (Formula presented.) for larger A/B values was more efficient in generating nucleation sites in the polar nanoregions (PNRs) than the (Formula presented.) for smaller A/B values, thereby providing greater dipole polarization. Consequently, the figure of merit, FOM, reached its maximum of 250 at A/B=0.9875, which was ca. 155% higher than that of the stoichiometric BST.

Original languageEnglish
Pages (from-to)1037-1043
Number of pages7
JournalJournal of the American Ceramic Society
Volume100
Issue number3
DOIs
Publication statusPublished - Mar 1 2017

Keywords

  • ferroelectricity/ferroelectric materials
  • microwaves
  • polarization

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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