Unraveling the Structural, Dielectric, Magnetic, and Optical Characteristics of Nanostructured La2NiMnO6 Double Perovskites

Abstract

Double perovskite La2NiMnO6 (LNMO) nanoparticles and nanorods were synthesized via a hydrothermal process, where only aqueous inorganic solvents are used to regulate the microscopic morphology of the products without using any organic template. They crystallized in a monoclinic (P21/n) double perovskite crystal structure. The LNMO nanoparticles exhibited spherical morphology with an average particle size of 260 ± 60 nm, and the LNMO nanorods had diameters of 430 ± 120 nm and length about 2.05 ± 0.65 μm. Dual chemical oxidation states of the Ni and Mn ions were confirmed in the LNMO samples by X-ray photoelectron spectroscopy. Strong frequency dispersion dielectric behavior observed in the LNMO ceramics, is attributed to the space charge polarization and the oxygen vacancy induced dielectric relaxation. A ferroelectric—paraelectric phase transition appearing near 262 K (or 260 K) in the LNMO ceramics prepared from nanoparticles (or nanorods) was identified to be a second-order phase transition. The LNMO samples are ferromagnetic at 5 K but paramagnetic at 300 K. The LNMO nanoparticles had larger saturation magnetization (MS = 6.20 μB/f.u. @ 5 K) than the LNMO nanorods (MS = 5.68 μB/f.u.) due to a lower structural disorder in the LNMO nanorods. The semiconducting nature of the nanostructured LNMO with an optical band gap of 0.99 eV was revealed by the UV–visible absorption spectra. The present results enable the nanostructured LNMO to be a promising candidate for practical spintronic devices.

B-site disorder driven Griffiths-like phase and electrochemical behavior in Y2NiCrO6 double perovskite

“…The mixed valence states of Ni and Cr result 7 distinct interactions, Ni 2+ 3+ , and Ni 3+ -O 2--Cr 3+ [7,75]. According to the Goodenough-Kanamori superexchange rule, the first six interactions will promote AFM, whereas only Ni 3+ -O 2--Cr 3+ will prefer FM interaction [16,75]. This mixed valance states are an indication of the absence of longrange ordering and presence of ASD in this type of double perovskites [7,[9][10][11].…”

“…Moreover, we have observed from XPS analysis a mixed cationic states of Ni and Cr ions. The mixed valence states of Ni and Cr result 7 distinct interactions, Ni 2+ 3+ , and Ni 3+ -O 2--Cr 3+ [7,75]. According to the Goodenough-Kanamori superexchange rule, the first six interactions will promote AFM, whereas only Ni 3+ -O 2--Cr 3+ will prefer FM interaction [16,75].…”

“…This difference between theoretical and experimental observation can be attributed to the large ASD as well as oxygen vacancies in the YNCO perovskite [28]. We have used the theoretical and experimental values of M S to calculate the ASD using the following equation [9,75,77]:…”

High-Efficiency Lead-Free La2NiMnO6-Based Double Perovskite Solar Cell by Incorporating Charge Transport Layers Composed of WS2, ZnO, and Cu2FeSnS4

“…A nonperovskite crystal structure is formed when the tolerance factor exceeds 1 or falls below 0.8, rendering it unsuitable for PV applications . The tolerance factor regarding double perovskite substance can be defined as eq : t = r A + r O 2 [ r normalB ′ + r normalB ″ 2 + r normalO ] where r A , r B′ , r B″ , and r O symbolize the ionic radii of A, B′, B″, and O ions, correspondingly. The tolerance factor is employed in the synthesis and development of novel, stable perovskite constructions through the formulation of perovskite compositions.…”

“…22 A nonperovskite crystal structure is formed when the tolerance factor exceeds 1 or falls below 0.8, rendering it unsuitable for PV applications. 23 The tolerance factor regarding double perovskite substance can be defined as eq 1 24 :…”