Giant Electrostriction in Doped Bi2O3 Ceramics

Nimrod Yavo, Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel
Alaric Smith, School of Chemistry, University of Birmingham, Birmingham, UK
Peter R. Slater, School of Chemistry, University of Birmingham, Birmingham, UK
Igor Lubomirsky, Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel

Electrostriction is the property of a material to exhibit deformation proportional to the applied electric field. Electrostriction is described by a fourth rank tensor, M_ikjl, with the units of strain/field² (m²/V²). According to common wisdom, the higher the dielectric constant, ε, the larger is the strain. For ceramics with ε<100, M is usually within the range of 10^-21-10^-22 m²/V² . Commercial electrostrictors (often called relaxors like (1-x)[Pb(Mg_1/3Nb_2/3)O₃]-x[PbTiO₃], PMN-PT) have ε=10,000-20,000 and exhibit M»10^-16-10^-15m²/V².

We have recently reported that thin films of Gd-doped ceria exhibit M=10^-16-10^-17m²/V² though their dielectric constant is only ε≈30, which indicates that a fundamentally different mechanism is at work.

To test the generality of this finding we have investigated electrostriction in bulk ceramics of Bi₂O₃ doped with Nb and Y. These ceramics, similar to Gd-doped ceria, have a fluorite crystal structure, large concentration of oxygen vacancies and dielectric constant ε≈25-40.  We have found that these ceramics exhibit electrostriction coefficient (0.5-1.2)·10^-17m²/V², which increases with the concentration of vacant oxygen sites (14%-21.5%).

Our finding strongly suggest that fluorite-structured oxides with a large concentration of oxygen vacancies represent a fundamentally new class of electrostrictive materials.