Effect of oxygen annealing on the multiferroic properties of Ca2+ doped BiFeO3 nanoceramics

Abstract

The high leakage current in divalent ion doped BiFeO 3 systems is limiting their large scale application. It is clearly shown that the methodology of oxygen annealing will prove to be an effective procedure for suppressing the detrimental consequences that originate from the oxygen vacancies. The samples annealed under oxygen also show different particle morphologies and packing density that can help in tuning the relevant physical properties, viz., magnetic, ferroelectric, and magnetoelectric. The difference in magnetic behaviour in samples annealed in air and oxygen can be explained in terms of the modification in the Fe-O-Fe bonds, domain wall pinning centres, and crystal anisotropy. Another important observation is the stabilization of a dielectric anomaly near the magnetic transition temperature. This observation can make this multiferroic system very interesting for application in sensors where the change in the magnetic parameters can be observed by monitoring the electrical parameters. Detailed analysis of the dielectric and impedance curves indicate towards the presence of non-Debye type processes in samples obtained by annealing in air or oxygen. From the calculated activation energy values, the vacancy related relaxation mechanism is predominant in air annealed samples, while the oxygen annealed samples show the presence of two type of relaxation processes, viz., electron hopping mechanism stabilizes at low temperature while, at higher temperatures, the process associated with the diffusion of doubly ionized oxygen ions predominates. The ac-conductivity data suggests that the correlated barrier tunnelling mechanism, where single electron or two electrons hopping through neighbouring lattice sites leads to ac-conduction. V C 2014 AIP Publishing LLC.

Dielectric relaxations and electrical properties of Aurivillius Bi3.5La0.5Ti2Fe0.5Nb0.5O12 ceramics

“…Where, A is pre-exponential factor and n (1>n>0) determines the departure from ideal capacitor (Debye behavior). For n=0, Q behaves perfectly resistive and for n=1, it behaves as an ideal capacitor [23]. The simulation clearly indicates the presence of two relaxations.…”

“…4(b). C is the capacitance, R is the resistance and Q is the constant phase element (CPE) which is the modified capacitance of BLTFN ceramics having impedance Z* CPE =[A(jω) n ] -1 [23]. Where, A is pre-exponential factor and n (1>n>0) determines the departure from ideal capacitor (Debye behavior).…”

Effect of Fe/Ta doping on structural, dielectric, and electrical properties of Bi4Ti2.5Fe0.25Ta0.25O12 ceramics

“…Where R and C are the resistance and capacitance of the elements, respectively, and Q is the constant phase element (CPE) of the circuit. CPE represents the modified capacitance of the ceramics materials having impedance Z* CPE = [ A (j ω ) n ] −1 . In the equation, A is pre‐exponential factor and n is the empirical exponent, indicates the departure from Debye behavior and its values varies from 0 to 1; Q perform as perfect resistive nature for n=0 and operate as an ideal capacitor for n=1 .…”

“…44 In the equation, A is pre-exponential factor and n is the empirical exponent, indicates the departure from Debye behavior and its values varies from 0 to 1; Q perform as perfect resistive nature for n=0 and operate as an ideal capacitor for n=1. 44 What is the main contribution to the single relaxation, grains or grain boundaries or simply the bulk? As known that complex impedance data only highlight the more dominant resistive element of the microstructural components, 45 therefore, the only interpretation of complex impedance data is insufficient for the correct understanding of relaxation behaviors in BTFT ceramics.…”

Phase relations and ionic transport behaviour in new mixed oxides of ceria–zirconia–gadolinia

“…The idea was to examine the effect of introduction of anion vacancies on the lattice, already bestowed with high mobility of oxide ions, on the ionic conductivity. The presence of oxygen vacancies, in general, is known to possess a great influence over the response of the material to electrical stimuli [10]. Recently several studies on ionic conductivity behavior of ceria based mixed oxides have been reported [11][12][13].…”