Dielectric Relaxation in Sr(Co1/3Nb2/3)O3 Compound – A Candidate For Microwave Applications

Abstract

Relaxor ferroelectric compounds Sr(B1/3Nb2/3)O3, where (B = Mg2+, Co2+, Cu2+), synthesized by standard so-lid state reaction technique, exhibit strong correlation between structure, dielectric and transport behavior. The structure changes from highly distorted monoclinic structure in Mg2+ and Co2+ substituted samples to partially distorted Tetragonal structure in Cu substituted samples. In Cu2+ based system significant Jahn- Teller distortion induced enhancements in dielectric properties have also been observed. Further, weak Jahn- Teller distortion due to unevenly occupied t2g levels in Co2+ produces intermediate rise in ε' as well as inbuilt flexibility to conduction electron movement enhances dielectric loss (tan δ). On the other hand, strong Jahn-Teller effects in Cu2+ substituted compound, due to unevenly occupied eg levels, results in large enhancement in ε' and frequency exponent ‘s’ ( 500 at 300 K temperature & at 10 KHz frequency). The UV-Vis studies give the wide energy band gap semi conducting values {Eg ≥ 3.00 eV}. The improved physical properties of Sr(Cu1/3Nb2/3)O3 compound makes it suitable for energy storage devices as well as microwave device applications at wide frequency range.