The sintering behavior of CeO2-doped strontium barium niobate ceramics

Defects, Structure Changes, and the Effect of Random Fields on the Displacement of Off‐Center Ions in Sr0.5Ba0.5Nb2O6 Doped with Combinations of Ce and Cr

“…The defect reactions of undoped and Cr‐doped SBN50 had been determined via the study of the sintering behavior 34,35 . However, the conclusion drawn previously concerning the charge‐compensating defect of Ce‐doped SBN50 36 was misinterpreted and needs to be reassessed. In this investigation, the samples have been carefully prepared to assure that the dopants have completely dissolved in SBN50 without the presence of second phases, as evidenced in Fig.…”

Charge‐Compensating Defect in Ceria‐Doped Strontium Barium Niobate by Electron Energy‐Loss Spectroscopy and X‐ray Photoelectron Spectroscopy

“…Moreover, because the niobium ion has been suggested as a rate-limiting species during the sintering of SBN ceramics, 20 the creation of niobium vacancies leads to the increase of the densification rate, which, however, is contradictory to the densification behavior found in the previous work. 13 Therefore, the development of niobium vacancy for the charge compensation should be excluded. Furthermore, if a strontium-ion vacancy (V Sr ЈЈ ) or barium-ion vacancy (V Ba ЈЈ ) is created, it contracts the A-site space, which, in turn, enlarges the neighboring NbO 6 octahedral unit; i.e., the Nb-O bond is lengthened, and, thus, Nb-O bond strength decreases.…”

“…Therefore, the diffusion of the niobium ion becomes easier in the structure, i.e., the activation energy of diffusion decreases, which, however, contradicts the result that CeO 2 dopant increases the activation energy of SBN sintering. 13 Based on the above discussion, the creation of a strontium or barium vacancy for charge compensation also is impossible.…”

“…Therefore, the Nb-O bond strength in the octahedral unit of NbO 6 increases, which, in turn, decreases the diffusivity of the niobium ion and increases the activation energy in sintered SBN ceramics, consistent with the observation in the previous work. 13 Besides, based on SBN structure, when more oxygen ions occupy the empty O(4) and O(5) sites, the c-axis lattice parameters decrease but the a-axis lattice parameters increase because of the coulomb attraction between the oxygen ion in the O(4) and O(5) sites and the niobium ion and because of the repulsion of the oxygen ion between O(4) and oxygen. 1 This viewpoint is evidenced in Fig.…”

“…Moreover, cerium doping is also known to enhance the relaxor feature of SBN. [12][13][14][15] Therefore, the defects induced by cerium doping in SBN are worth investigation. In the previous work, 13 it has been suggested that the possible charge-compensated defect for cerium doping in SBN ceramics might be an excessive oxygen ion occupying the vacant O(4) or O(5) site.…”