Influence of A-site deficiency on structural evolution of Pr2-xNiO4+δ with temperature

Structure, electrical conductivity and oxygen transport properties of Ruddlesden–Popper phases Lnn+1NinO3n+1 (Ln = La, Pr and Nd; n = 1, 2 and 3)

“…20 SOFCs with cathode materials of La 2 NiO 4+d and Nd 2 NiO 4+d show no degradation in cell performance aer hundreds of hours of operation at 750-800 C. 21,22 Pr 2 NiO 4+d , on the other hand, starts to decompose upon annealing in air above 580 C to a mixture consisting of Pr 4 Ni 3 O 10Àd , PrNiO 3Àd and Pr 6 O 11 . [23][24][25][26][27][28][29][30][31] Though apparent oxygen diffusion and surface exchange kinetics are enhanced aer thermal decomposition, 23 a signicant degradation of cell performance is observed for the SOFC with Pr 2 NiO 4+d as the cathode aer 1000 h of operation at 750 C. 22 Meanwhile, there is a growing interest in using higher order RP nickelates as the cathode material. Among the n ¼ 2 members, Ln 3 Ni 3 O 7Àd (Ln ¼ La, Pr, Nd), so far only La 3 Ni 2 O 7Àd could be prepared in a phase-pure form, while Pr 3 Ni 2 O 7Àd and Nd 3 Ni 2 O 7Àd have been observed only as disordered intergrowths in the corresponding n ¼ 3 members.…”

Improving Electrocatalytic Activity of Cobalt-Free Barium Ferrite-Based Perovskite Oxygen Electrodes for Proton-Conducting Solid Oxide Cells via Introducing A-Site Deficiency

“…For A-site-deficient Pr 2−x NiO 4+δ with a K 2 NiF 4 structure, the neutron diffraction and thermogravimetric analysis confirmed that the Pr deficiency could generate the lattice oxygen vacancy at the equatorial and apical sites. 19 While the A-site deficiency strategy has been widely applied in improving the oxygen electrode for oxygen-ion-conducting SOCs, it is rarely reported in the research of protonconducting SOCs.…”

Intolerance of the Ruddlesden–Popper La2NiO4+δ Structure to A-Site Cation Deficiency

“…46,47 Noteworthily, it was reported that the occupancy of interstitial oxygen sites in the rock-salt-type layers remains nearly constant, while the occupancy of equatorial and particularly apical oxygen sites in the perovskite layers decreases with increasing x. 46,47 The prepared Pr 2−x NiO 4+δ ceramic samples were demonstrated to show lower electrical conductivity but higher oxygen diffusion and surface exchange coefficients at 450−575 °C compared to the parent Pr 2 NiO 4+δ . 47 The initial intention of the present work was to prepare a series of RP-type La 2−x NiO 4+δ nickelates with a gradual change from oxygen excess to oxygen deficiency and to perform a comparative investigation of oxygen-ionic transport occurring by different ion-diffusion mechanisms.…”

“…XRD and neutron diffraction (ND) revealed the presence of PrO y and NiO phase impurities in both materials; the fractions of secondary phases increased with x . Nonetheless, based on the results of electron probe microanalysis and Rietveld refinement of ND data, it was concluded that synthesized Pr 2– x NiO 4+δ are still A-site-deficient, although the actual concentration of A-site vacancies is ∼2 times lower compared to the nominal one. , Noteworthily, it was reported that the occupancy of interstitial oxygen sites in the rock-salt-type layers remains nearly constant, while the occupancy of equatorial and particularly apical oxygen sites in the perovskite layers decreases with increasing x . , The prepared Pr 2– x NiO 4+δ ceramic samples were demonstrated to show lower electrical conductivity but higher oxygen diffusion and surface exchange coefficients at 450–575 °C compared to the parent Pr 2 NiO 4+δ …”

“…29,30 These findings inspired the studies of Nd 1.95 NiO 4+δ as a cathode material for intermediate-temperature SOFCs. 30−33 Ning et al 46,47 prepared Pr 2−x NiO 4+δ (x = 0.1 and 0.2) samples by solid-state synthesis at 1200 °C. XRD and neutron diffraction (ND) revealed the presence of PrO y and NiO phase impurities in both materials; the fractions of secondary phases increased with x.…”