Crystal structure of the high temperature phase of oxidised Pr2NiO4+δ

Oxygen Exchange in Pr2NiO4+δ at High Temperature and Direct Formation of Pr4Ni3O10−x

“…This loss of oxygen is small and occurs at a constant rate with ¹ between 470 and 8503C where the composition reaches Pr NiO . A small anomaly is observed at 4703C attributed previously to an order}disorder phase transition involving interstitial oxygen (16).…”

“…Pr NiO can incorporate excess oxygen up to an extent controlled by structural strains (3,15). In the pure compound, at high temperature, both oxygen excess and high thermal motion cause the apical oxygen to split into two sites leading to a statistical density map with a peanut shape (16). This suggests an intrinsic instability of this oxidized layer of &&PrO W ''.…”

Molecular dynamics study of oxygen diffusion in Pr2NiO4+δ

“…A perfect match of these layers would result in the tetragonal I4/mmm space group. 18 However, there is considerable mismatch between these layers and therefore significant stress in the unrelaxed case. The interlayer mismatch promotes the formation of oxygen interstitials in the Pr 2 O 2 bilayers.…”

“…17,18 At temperatures below 720 K Pr 2 NiO 4+d transforms into an orthorhombic symmetry. 19 The structure of Pr 2 NiO 4 in its tetragonal form is illustrated in Fig.…”

Temperature Measurement: Christiansen Wavelength and Blackbody Reference

“…To make pyrometric calibrations at higher temperature with larger thin plates, we have first investigated the chemical stability of this oxide up to 1600 K. Thermogravimetric analysis (TGA) measurements of powder have been made with a symmetrical balance of high sensitivity (TGA 24-24, Setaram, Lyon, sensitivity ±1 µg) to follow the oxygen overstoichiometry evolution (δ) [13]. We have analyzed a fine black powder obtained before by following a modified sol-gel route [14].…”