The Semiconductor-to-Metal Transition in Question in La2-xNiO4+δ (δ > 0 or δ < 0)

Metal–Semiconductor Transition of La2NiO4+δ

“…However, in the range 550-1273 K, the concentration decreased with increasing temperature and slightly increased with increasing initial oxygen pressure. The initiating temperature of the oxygen loss at around 570 K agrees well with the temperature of the resistivity minima of La NiO >B reported by Odier et al (16) and by us in this paper. The degree of the oxygen loss is suppressed by increasing the oxygen pressure, but the degree of the suppression is not very large under the experimental conditions (Fig.…”

“…They pointed out that oxygen loss occurs in La \V NiO >B and Pr NiO >B above 600 K (19,30) and concluded that the minimum of resistivity of La \V NiO >B and Pr NiO >B around 600 K is due to oxygen loss (19). A model of the metal-semiconductor transition of La \V NiO >B was also proposed by them (16). Figure 1 presents unpublished data.…”

“…1). Detection of oxygen variation in situ as a function of temperature and oxygen pressure is absolutely necessary, as Odier et al had carried out with a thermobalance (16,19,30).…”

Properties of Copper Doped Neodymium Nickelate Oxide as Cathode Material for Solid Oxide Fuel Cells

“…as the temperature increased in the low temperature range (300~500ºC) and thereafter decreased. It appears that this phenomenon results from the typical semiconductor-to-metal transition at the high temperature [15][16][17][18]. On the other hand, the Nd 2 CuO 4+δ sample exhibited the typical temperature dependence which can be observed in oxide semiconductors, i.e., the conductivity increased with increasing the temperature.…”

“…The electronic state of La 2−x Sr x CuO 4+δ becomes a localized or itinerant state depending on the copper mean valence. The transition of the electronic state takes place at the copper mean valence of around 2.05 at 800 and 900ºC, and the electronic state of La 2−x Sr x NiO 4+δ takes place at the nickel mean valence between 2.1 and 2.4 at 600 and 800ºC [8,17,21]. Thus Nd 2 NiO 4+δ will have more excess oxygen content than Nd 2 CuO 4+δ , because Ni mean valence is higher than Cu.…”