Bismuth pyrochlore films for dielectric applications

Wei Ren, Ryan Thayer, Clive A. Randall, Thomas R. Shrout, Susan E. Trolier-McKinstry

Research output: Contribution to journalConference articlepeer-review

11 Scopus citations


Bismuth pyrochlore ceramics have modest temperature coefficients of capacitance, good microwave properties, and can be prepared at relatively modest temperatures (approx. 900 - 1100°C). This work focuses on the preparation and characterization of thin films in this family for the first time. A sol-gel procedure using bismuth acetate in acetic acid and pyridine, in combination with zinc acetate dihydrate and niobium ethoxide in 2-methoxyethanol was developed. The solution chemistry was adjusted to prepare (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 and Bi2(Zn1/3Nb2/3)2O7 films. Solutions were spin-coated onto platinized Si substrates and crystallized by rapid thermal annealing. In both cases, crystallization occurred by 550°C into the cubic pyrochlore structure. (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 films remained in the cubic phase up to crystallization temperatures of 750°C, while the structure of the Bi2(Zn1/3Nb2/3)2O7 thin films is dependent of the firing temperature: cubic below 650°C and orthorhombic above 750°C. A mixture of cubic and orthorhombic structures is found at 700°C. The resulting BZN films are dense, uniform, and smooth (rms roughness of < 5 nm). Cubic bismuth zinc niobate films show dielectric constants up to 150, a negative temperature coefficient of capacitance, TCC, (approx. - 400 ppm/°C), tan δ < 0.01, and a field tunable dielectric constant. Orthorhombic films showed smaller dielectric constants (approx. 80), low tan δ (< 0.01), positive TCC, and field independent dielectric constants. TCC could be adjusted to new 0 ppm/°C using a mixture of orthorhombic and cubic material.

Original languageEnglish (US)
Pages (from-to)137-142
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
StatePublished - 2000
EventMaterials issues for Tunable RF and Microwave Devices - Boston, MA, USA
Duration: Nov 30 1999Dec 2 1999

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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