Localization length-doping dependence in GdBa2Cu3−xCrxO7−δ

Charge carrier localization and metal to insulator transition in cerium substituted (Bi,Pb)-2212 superconductor

“…Mott has experimentally verified the VRH mechanism at low temperatures, in a class of systems and treatise his observations. Such trends have been reported in the insulating phases of high-T C materials too, like the GdBa 2 Cu 3−x Cr x O 7+ı system [10].…”

“…HTSCs are examples of homogeneous systems and in recent years the rare-earth (RE) substitution studies in HTSCs have attracted considerable attention. It has been reported that different aliovalent substitutions or changes in the oxygen stoichiometry can effectively alter the concentration of carriers in the HTSC systems, resulting in a MIT [8,[10][11][12]. MIT can also be caused by photo-induced laser treatment in which the photo-induced electron-phonon anharmonicity plays a crucial role in the transition [13].…”

Detailed analysis on electrical conduction transition from 2D variable range hopping to phonon-assisted 3D VRH mechanism belonging to Bi-site La substituted Bi-2212 system

“…1 and 2 with assuming the Fermi energy value of about 10 22 eV -1 cm -3 [56], and the results obtained are numerically provided in La atoms localize the mobile holes in the crystal structure due to the increase of the effective disorders in the system. Moreover, it would be more precise to say that the disorders appeared cause to the formation of polarons in the system [57]. This is attributed to the fact that the symmetry of the ordered system is broken at the molecular scale, and so the localized states in band tails are extensively formed by the states of valence and conduction bands within the more required energy [25,51].…”

“…Hence, the hopping conductivity mechanism contributes to the electrical conduction by the mediated phonons from one filled state to an empty state. This phenomenon is even valid for the crystalline materials in the presence of small range order [57]. The following equations are used for the determination of R and ∆W values belonging to the compounds exhibiting MIT characteristics in this comprehensive work [46,48].…”

Solubility limit of tetravalent Zr nanoparticles in Bi-2223 crystal lattice and evaluation of fundamental characteristic properties of new system

“…It is apparent from the table that the enhancement in the Zr addition level leads to expand the a-axis length values but contract in the c cell parameter as a result of the partial replacement of tetravalent Zr inclusions for the divalent Cu nanoparticles in the Bi-2223 system. Namely, the presence of the different aliovalent substitutions through the Bi-2223 crystal structure results in the positive charge in the oxygen deficient Bi-O double layers, and so the positive charge appeared needs to be balanced by the valency/oxygen for the charge neutrality [24][25][26][27][28]. Hence, the interlayer distances between the Cu-Ca-Cu and Ca-Sr sites in the layered structure enlarge; however, the interlayer spaces of the Sr-Bi, Bi-Bi and Sr-Bi-Bi-Sr sites shorten automatically, so does c cell parameter [29].…”