High‐Temperature Electrical Conductivity of LaCr_1−xCo_xO₃ Ceramics

Abstract

LaCr1−xCoxO3 solid‐solution ceramics (x = 0.0–0.3) were prepared by pressureless sintering of a submicrometer powder. The powder was synthesized by a modified glycine nitrate process at 800°C. The electrical conductivity of the material sintered at 1600°C was measured by AC four‐wire method from room temperature to 1200°C. While undoped (x = 0) LaCrO3 revealed semiconductivity dominated by thermally activated mobility of small polarons over a vast temperature range, substitution of Co for Cr gave rise for a pronounced enhancement of conductivity at temperatures >200°C. XPS analysis showed that the concentration of Cr4+ on the Cr‐site and Co2+ at the Co‐site increased with Co substitution suggesting a thermally activated redox reaction Cr3+ + Co3+→Cr4+ + Co2+ to create additional charge carriers. Thus, Co doping offers a high potential for designing the electrical conductivity making LaCr1−xCoxO3 an interesting resistivity material for high temperature applications.

High‐Performance and Stable Silicon Photoanode Modified by Crystalline Ni@ Amorphous Co Core‐Shell Nanoparticles

“…No Ni 2p 3/2 XPS signal was observed on n‐Si/SiO x /Ni@Co. After ion milling of about 10 nm, the sample exhibits strong metallic Ni 2p 3/2 (852.4 eV) and metallic Co 2p 3/2 (778.2 eV) XPS peaks, demonstrating the conformal Co shell on Ni core (Figure S3a and S3b). Note that the XPS analysis on the shell without ion milling exhibited the existence of Co 2+ species with a binding energy of 780 eV and O 2− species with a binding energy of 529.6 eV, suggesting that the amorphous shell was composed of CoO (Figure S3b) . These evidences revealed that a naturally oxidized layer formed in the amorphous Co shell, probably due to its high activity.…”

“…As shown in Figure S3d, after a long‐period CV scanning on n‐Si/SiO x /Ni@Co photoanode, the binding energy of the Co species moves from 780 to 780.5 eV, and meanwhile, the energy splitting between the Co 2p 1/2 and Co 2p 3/2 levels narrows from 15.7 to 15 eV, clearly demonstrating the transformation of Co 2+ to Co 3+ species ( i. e . CoOOH) ,,. This evidence indicated that, during the OER, the amorphous CoO or Co is easily oxidized to Co 3+ in CoOOH.…”

Synthesis and Electrochemical Properties of LaCr1−xCoxO3 (0 ≤ x ≤ 0.5) via Co-precipitation Method

“…Electrode reactions over the surface of the oxides under atmospheric pressure exhibit high currents, revealed an increasingly of Cr 4? ions as the Co content increased which act as holes source [11]. The electrochemical oxidation corresponds to the reaction:…”

“…The critical point of this synthesis is the presence of nitrate in the combustion reaction, which in larger quantities, where the problem lies in the decomposition of nitrate anions with violent NO 2 , production which is especially observed in a large scale preparations during the evaporation of the solvent [10]. Recently, Bonet et al [11] have obtained LaCr 1-x Co x O 3 solid-solution synthesized by a modified glycine nitrate process at 800°C ceramics for the limited composition range (x = 0.0-0.3) and measured the electrical conductivity of these materials sintered at high temperatures.…”

Characteristics of Nano-Size LaCrO3 Prepared Through Sol-Gel Route Using Pectin as Emulsifying Agent

“…The existence of Cr-O bond is indicated by the absorption bands located centered at 857.76 cm -1 for the sample calcined at 600 o C and that centered at 883.27 cm -1 in the sample calcined at 700 o C, which were assigned to stretching vibration of the bond. These stretched vibrations are not coming from the pure O-Cr-O bond which is located at 783 cm -1 61,62 . The presence of this bond was also supported by the La-O-La absorption bands associated with bending vibration, located at around 617.77, 621.29, and 627.79 cm -1 for sample calcined at 600, 700, and 800 o C and a pure La-O-La stretching vibration located at 620 cm -1 63 .…”