Infrared reflection study of two-dimensional structural phase transition in stoichiometric Pr2NiO4

La and Sr Substituted Pr2NiO4+δ: Oxygenation and Electrical Properties

“…Several mechanisms can relax the strain. In oxygen stoichiometric compounds, the tilting of NiO octahedra triggers structural transitions (10)(11)(12). On the other hand, the introduction of extra oxygen in the rock salt layer fills the space and lowers the structural strain.…”

High-temperature behavior of infrared conductivity of aPr2NiO4+δsingle crystal

“…In many conducting oxides, the following expression of the dielectric response has been used successfully to reproduce their peculiar optical features over several decades of frequencies: [22][23][24]35,36,38,40,44,45,51 …”

“…In Pr 2 NiO 4+␦ , the oxygen overstoichiometry ␦ plays a crucial role on its physical and structural properties, [22][23][24][25][26][27][28][29] since insertion of oxygen relaxes the constraints of the undoped distorted compound and creates holes in the NiO 2 planes, [25][26][27] inducing highly anisotropic behavior. 22,24 Pr 2 NiO 4+␦ undergoes a structural phase transition from an orthorhombic symmetry ͑LTO͒ to a tetragonal one ͑HTT͒ at T ϳ 720 K, 26 accompanied by oxygen loss.…”