@conference{
author = "Vukašinović, Jelena and Počuča-Nešić, Milica and Luković Golić, Danijela and Branković, Zorica and Dapčević, Aleksandra and Branković, Goran",
year = "2018",
abstract = "Perovskite type ceramic materials with general formula
ABO3 are very important class of materials due to their
various chemical and physical properties. They have wide
applications such as electrode material for solid state fuel
cells (SOFC), capacitors, resistors, superconductors,
catalysts, electrolytes, microwave devices, and
magnetoresitant materials [1, 2]. Lanthanum nickelate
(LaNiO3, LNO) is a ternary oxide with rhombohedrally
distorted perovskite lattice. In LNO trivalent nickel ions
(Ni3+) are in low spin configuration (t2g
6eg
1) and the
conduction band is formed by the hybridization of the egorbitals
of Ni3+ and the p-orbitals of oxygen. As a result,
LNO shows metallic n-type conductivity in wide temperature
range [3].
For this reason LNO has been proposed as a cathode material
for intermediate-temperature SOFCs (IT-SOFCs) with
operating temperature range of 650-800 °C. The possible
dawbacks of LNO as a potential material for this application
are poor density and thermal unstability at temperatures
higher than 850 °C, when LNO starts gradually to decompose
into the lower oxides Lan+1NinO3n+1 (n = 3, 2, 1) and NiO.
Still, all of these La-Ni-O compounds exhibit high electronic
conduction within the NiO6 octahedra in their perovskite
layers and excellent oxygen ionic conductivity through
oxygen interstitials on the LaO rock-salt plane. Also, their
coefficient of thermal expansion (CTE) matches those of
materials commonly used as IT-SOFC electrolyte and anode
[1].
A possible use of LNO as a cathode for SOFC requires the
improvement of its thermal stability and enhancement of
density of ceramic samples. The aim of this work was to
fullfill these requirements by doping of lanthanum-nickelate
into the B site. Using transition metal of higher valency than
Ni3+ as a dopant, could enhance the electron concentration
and carrier mobility, which results in improvement of
electrical conductivity of ceramic material. Doping could also
influence the sintering process and improve the density of the
ceramic materials.
In this work we present dense ceramic materials of LaNi1-
xNbxO3 (x = 0.005, 0.05) prepared by mechanochemically
assisted solid state method. La2O3, NiO and Nb2O5, used as a
precursor reagents, were mechanochemically activated in the
planetary ball mill for 5 h. Obtained powders were calcined at
700 °C for 3h in air, and afterwards sintered at 900 °C and
1200 °C for 2 h and 10 h in different atmospheres (air and
oxygen).
The influence of Nb doping on electrical properties and
microstructure of LaNi1-xNbxO3 ceramic materials was
investigated. All samples were analyzed by X-ray diffraction
analysis (XRD), scanning electron microscopy (SEM) and
energy dispersive X-ray spectroscopy (EDS). Electrical
conductivity of ceramic LaNi1-xNbxO3 samples was measured
in different mediums and complete characterization of
electrical properties was performed.
The XRD analysis indicated the existence of secondary
phases Lan+1NinO3n+1 and NiO along with the rhombohedral
LaNiO3. Samples sintered at 900 °C in oxygen atmosphere
for 2 h had density of 64 % and 60 % for x = 0.005 and x =
0.05 (Fig. 1). The electrical conductivity was improved by
doping with Nb, and obtained values were 2.7 S cm and 2.6 S
cm for x = 0.005 and x = 0.05 at room temperature. The
obtained results confirmed that doping by Nb along with
sintering in oxygen atmosphere can improve electrical
conductivity, density, and thermal stability.
References
[1] R.K. Sharma, E. Djurado, J Mater Chem A, 5 (2017)
22277-22287.
[2].A. S. Bhalla, R. Guo, R. Roy, Mat Res Innovat, 4 (2000)
3-26.
[3] K. Sreedhar et al., Phys Rev B, 46 (1992) 6382-6386.",
publisher = "University of Belgrade, Vinča Institute of Nuclear Sciences, Hydrogen Economy Initiative Serbia, Belgrade",
journal = "3rd International Symposium on Materials for Energy Storage and Conversion, mESC-IS, September 10-12, 2018, Belgrade, Serbia",
title = "Synthesis and characterization of Nb-doped lanthanum nickelate La(Ni,Nb)O3",
pages = "78",
url = "https://hdl.handle.net/21.15107/rcub_rimsi_2034"
}
