Time–temperature superposition in the grain and grain boundary response regime of A₂HoRuO₆(A = Ba, Sr, Ca) double perovskite ceramics: a conductivity spectroscopic analysis

Abstract

The pursuit for an appropriate universal scaling factor to satisfy the time-temperature superposition principle for grain and grain boundary responses has been explored in the ac conductivity domain for polycrystalline double perovskite oxides A2HoRuO6 (AHR; A = Ba, Sr, Ca). The samples show different structural phases ranging from cubic to monoclinic with decreasing ionic radii. The degree of distortion in the materials is correlated to the strength of bonding through the bond valence sum (BVS). The conductivity spectra for all the samples obey the power law behaviour. The contribution of different microstructural features to the conduction process is established. Thermal variation of dc resistivity points towards a gradual crossover from nearest neighbour to variable range hopping. The activation energies obtained from dc conductivity, hopping frequency and relaxation frequency show close correlation between the conduction and relaxation mechanisms. The scaled conductivity curves for AHR showed the presence of two different conduction processes with dissimilar activation energies in the grain boundary and grain response regimes. It is thus concluded that a single scaling parameter is insufficient to satisfy the time temperature superposition principle universally when two different thermally activated regions are present simultaneously in the materials.

The electrical modulus and other dielectric properties by the impedance spectroscopy of LaCrO3and LaCr0.90Ir0.10O3perovskites

“…The long-range fundamental conductivity results in exact overlapping of the modulus and impedance peaks. [24][25][26][29][30][31][32][33][34] Especially, the investigation of electrical properties of these materials 27,28 can provide us an insight for their application in sensors, optical memory, electro-optic devices and actuations in the microelectromechanical systems etc.…”

Summerfield scaling model and electrical conductivity study for understanding transport mechanisms of a Cr3+ substituted ZnAl2O4 ceramic

“…For disordered solids, this scaling characteristic is the time–temperature superposition principle (TTSP). 59,60 The scaling mechanism of experimental conductance isotherms is presented by a general formula: 61,62 where σ dc is the dc conductance, ν H is the hopping frequency and F is the temperature-independent function. The scaled conductance spectra for the synthesized compound at different temperatures are shown in Fig.…”

Dielectric relaxation of the double perovskite oxide Ba2PrRuO6

“…The morphology and grain size are similar to that reported previously for Ba 2 HoRuO 6 . 25 The real part of dielectric permittivity 3 0 as a function of temperature T at selected test frequency f for Ba 2 PrRuO 6 between 10 K and 300 K are depicted in Fig. 2(a).…”