Structural manipulation and tailoring of dielectric properties in SrTi1-xFexTaxO3 perovskites: Design of new lead free relaxors.

R Shukla,A K Tyagi,J Gopalakrishnan,S K Deshpande,A B Shinde,S N Achary,P S R Krishna,S J Patwe

doi:10.1038/srep23400

Abstract

We report composition dependent structure evolution from SrTiO3 to SrFe0.5Ta0.5O3 by powder X-ray and neutron diffraction studies of SrTi1−2xFexTaxO3 (0.00 ≤ × ≤ 0.50) compositions. Structural studies reveal cubic (Pm3m) perovskite-type structure of the parent SrTiO3 for x up to 0.075 and cation disordered orthorhombic (Pbnm) perovskite-type structure for x ≥ 0.33. A biphasic region consisting of a mixture of cubic and orthorhombic structures is found in the range for 0.10 ≤ × ≤ 0.25. Dielectric studies reveal transformation from a normal dielectric to relaxor like properties with increasing Fe3+ and Ta5+ concentration. Dielectric response is maximum at x = 0.33 in the series. The results establish a protocol for designing new lead-free relaxor materials based on the co-substitution of Fe3+ and Ta5+ for Ti4+ in SrTiO3. A complex interplay of strain effects arising from distribution of cations at the octahedral sites of the perovskite structure controls the dielectric properties.

Highlights

In rutile-type TiO2 has been achieved in lightly doping of In3+ and Nb5+ at Ti4+ site[19]
In a similar strategy to prepare new ferroelectric materials in an otherwise incipient ferroelectric SrTiO3, we explored SrTi1−2xFexTaxO3 system and the results are presented in this manuscript
As no distinct features attributable to cation ordering observed in the X-ray diffraction (XRD) data as well as neutron diffraction (ND) data explained later in this manuscript, we infer an orthorhombic cation disordered perovskite structure for x = 0.5 composition

Summary

Introduction

In rutile-type TiO2 has been achieved in lightly doping of In3+ and Nb5+ at Ti4+ site[19]. As no distinct features attributable to cation ordering observed in the XRD data as well as neutron diffraction (ND) data explained later in this manuscript, we infer an orthorhombic cation disordered perovskite structure for x = 0.5 composition. In the single phase cubic and the orthorhombic phase regions a systematic increasing trend in unit cell volume with increasing Fe3+ and Ta5+ content is observed, which can be attributed to the larger ionic radii of Fe3+ and Ta5+ (rFe3+ = 0.645 Å and rTa5+ = 0.64 Å, in octahedral coordination) compared to Ti4+ ions

Results

Conclusion