TY - JOUR

T1 - High-temperature behavior of calcium substituted layered neodymium nickelates

AU - Pikalov, S. M.

AU - Vedmid, L. B.

AU - Filonova, E. A.

AU - Pikalova, E. Yu

AU - Lyagaeva, J. G.

AU - Danilov, N. A.

AU - Murashkina, A. A.

N1 - Publisher Copyright: © 2019 Elsevier B.V.

PY - 2019/9/15

Y1 - 2019/9/15

N2 - Layered lanthanide nickelates of the first order with a K2NiF4-type structure, including Nd2NiO4, are considered as prospective oxygen electrode materials for different high-temperature electrochemical devices, membrane materials and catalysts. The presence of highly-mobile over-stoichiometric oxygen in their structure, the content of which depends on the synthesis and ambient conditions, strongly influences their functional properties. In this study, the materials of the Nd2-xCaxNiO4+δ (x = 0–1.0) series were obtained via a citrate-nitrate method. The Ca substitution limit was found to be equal to 30 mol %. The high-temperature structural, thermo-mechanical and electrical properties of the materials obtained were investigated in close relation with their oxygen over-stoichiometry. It was found that the absolute oxygen content decreased with Ca doping, which resulted in a transition from an orthorhombic structure (Fmmm sp. gr.) at x = 0, 0.1 to a tetragonal structure (I4/mmm sp. gr.) at x = 0.2, 0.3 and then, with further increase in Ca doping, to an orthorhombic structure (Bmab sp. gr.). Dilatometric curves for all the samples possessed high-temperature breaks corresponding to the structural changes caused by oxygen release upon heating, which was revealed in the HT-XRD and TGA-DSC experiments. There was a tendency for the thermal expansion coefficient to decrease both in the low and high temperature range with Ca doping. The minimum average TEC values were found for the samples with x = 0.4 (12.1 × 10−6 K−1) and with x = 0.6 (11.8 × 10−6 K−1) according to the HT-XRD and dilatometry data, respectively. There was a maximum at x = 0.4 (135 S cm−1) on the concentration dependence of the total conductivity obtained in the dc four-probe measurements. Materials with a medium Ca content (0.3–0.4), possessing moderate CTE values (∼12 × 10−6 K−1), close to those of the majority of solid-state electrolytes, and showing a high level of total conductivity, can be recommended as promising materials for various electrochemical applications.

AB - Layered lanthanide nickelates of the first order with a K2NiF4-type structure, including Nd2NiO4, are considered as prospective oxygen electrode materials for different high-temperature electrochemical devices, membrane materials and catalysts. The presence of highly-mobile over-stoichiometric oxygen in their structure, the content of which depends on the synthesis and ambient conditions, strongly influences their functional properties. In this study, the materials of the Nd2-xCaxNiO4+δ (x = 0–1.0) series were obtained via a citrate-nitrate method. The Ca substitution limit was found to be equal to 30 mol %. The high-temperature structural, thermo-mechanical and electrical properties of the materials obtained were investigated in close relation with their oxygen over-stoichiometry. It was found that the absolute oxygen content decreased with Ca doping, which resulted in a transition from an orthorhombic structure (Fmmm sp. gr.) at x = 0, 0.1 to a tetragonal structure (I4/mmm sp. gr.) at x = 0.2, 0.3 and then, with further increase in Ca doping, to an orthorhombic structure (Bmab sp. gr.). Dilatometric curves for all the samples possessed high-temperature breaks corresponding to the structural changes caused by oxygen release upon heating, which was revealed in the HT-XRD and TGA-DSC experiments. There was a tendency for the thermal expansion coefficient to decrease both in the low and high temperature range with Ca doping. The minimum average TEC values were found for the samples with x = 0.4 (12.1 × 10−6 K−1) and with x = 0.6 (11.8 × 10−6 K−1) according to the HT-XRD and dilatometry data, respectively. There was a maximum at x = 0.4 (135 S cm−1) on the concentration dependence of the total conductivity obtained in the dc four-probe measurements. Materials with a medium Ca content (0.3–0.4), possessing moderate CTE values (∼12 × 10−6 K−1), close to those of the majority of solid-state electrolytes, and showing a high level of total conductivity, can be recommended as promising materials for various electrochemical applications.

KW - Ca-doping

KW - Ceramic membrane

KW - High-temperature behavior

KW - NdNiO

KW - Oxygen electrode

KW - Ruddlesden-Popper phase

UR - http://www.scopus.com/inward/record.url?scp=85067361874&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2019.05.349

DO - 10.1016/j.jallcom.2019.05.349

M3 - Article

AN - SCOPUS:85067361874

VL - 801

SP - 558

EP - 567

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

ER -