Pooja Y. Raval; Shrey K. Modi; Khayati G. Vyas; Priya L. Mange; Kunal B. Modi
Abstract
Temperature-dependent electrical transport characteristics of un-milled and high-energy ball-milled samples (3 h (70 nm), 6 h (55 nm) and 9 h (45 mm)) of Ni0.5Zn0.5Fe2O4 spinel ferrite were explored. A well-defined metal to semiconductor transition exhibited by all the samples has been construed ...
Read More
Temperature-dependent electrical transport characteristics of un-milled and high-energy ball-milled samples (3 h (70 nm), 6 h (55 nm) and 9 h (45 mm)) of Ni0.5Zn0.5Fe2O4 spinel ferrite were explored. A well-defined metal to semiconductor transition exhibited by all the samples has been construed in view of direct and superexchange cationic interactions and delocalization to localization of charge carriers on increasing temperature. The peak temperature (Tmax) was found to shift towards a higher temperature side on milling principally governs by the lattice vibration scattering and intrinsic excitation. The crystallite size reduction, enhancement in strain and sudden decrease in the formation and octahedral site occupancy of Fe 2+ ions on milling found responsible for the prodigious rise (~ 250 times) in normalized resistivity values for the sample comminuted for 9 h. The spectrum of energies corresponds to charge trapping centers that cause small bump (3 h milled sample) and sharp cusp (9 h milled sample) for T>Tmax. These materials may be found suitable for thermal cutoff switching applications.
Nimish H. Vasoya; Kiran G. Saija; Akshay R. Makadiya; Tushar K. Pathak; Urmila M. Meshiya; Pooja Y. Raval; Kunal B. Modi
Abstract
The compositional dependence of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity (ε*) and loss tangent (tan d) for Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0, 0.1, 0.2 and 0.3) spinel ferrite series was investigated over wide frequency (f = 20 Hz to 1 MHz) and ...
Read More
The compositional dependence of the real (ε') and imaginary (ε'') parts of complex dielectric permittivity (ε*) and loss tangent (tan d) for Mn0.7+xZn0.3SixFe2-2xO4 (x = 0.0, 0.1, 0.2 and 0.3) spinel ferrite series was investigated over wide frequency (f = 20 Hz to 1 MHz) and temperature (T = 300 K to 673 K) ranges. Frequency dependence of ε',ε'' and tan δ has been explained based on the two-layer model of dielectrics. The nonlinear relationship between ε'(f) and σ'(f) suggests multi-relaxation process and formation of a broad hump in ε'(f, T) plots indicates collective contributions from electrons and holes to the polarization. The scaling by normalized frequency (f/fc) and scaled frequency (f/σdc) are found successful for ε' in high-frequency regime only while scaling found successful for ε'' over the whole range of frequency. The suitability of various scaling parameters was also tested for the master curve generation. The co-existence of localized and delocalized relaxations is verified.
)