Nanocrystalline Antiferromagnetic High-κ Dielectric Sr2NiMO6 (M = Te, W) with Double Perovskite Structure Type

Abstract

Double perovskites have been extensively studied in materials chemistry due to their excellent properties and novel features attributed to the coexistence of ferro/ferri/antiferro-magnetic ground state and semiconductor band gap within the same material. Double perovskites with Sr2NiMO6 (M = Te, W) structure type have been synthesized using simple, non-toxic and costless aqueous citrate sol-gel route. The reaction yielded phase-pure nanocrystalline powders of two compounds: Sr2NiWO6 (SNWO) and Sr2NiTeO6 (SNTO). According to the Rietveld refinement of powder X-ray diffraction data at room temperature, Sr2NiWO6 is tetragonal (I4/m) and Sr2NiTeO6 is monoclinic (C12/m1), with average crystallite sizes of 49 and 77 nm, respectively. Structural studies have been additionally performed by Raman spectroscopy revealing optical phonons typical for vibrations of Te6+/W6+O6 octahedra. Both SNTO and SNWO possess high values of dielectric constants (341 and 308, respectively) with low dielectric loss (0.06 for SNWO) at a frequency of 1 kHz. These values decrease exponentially with the increase of frequency to 1000 kHz, with the dielectric constant being around 260 for both compounds and dielectric loss being 0.01 for SNWO and 0.04 for SNTO. The Nyquist plot for both samples confirms the non-Debye type of relaxation behavior and the dominance of shorter-range movement of charge carriers. Magnetic studies of both compounds revealed antiferromagnetic behavior, with Néel temperature (TN) being 57 K for SNWO and 35 K for SNTO.

Structural, optical and dielectric properties of tellurium-based double perovskite Sr2Ni1−xZnxTeO6

“…Dependency of ε ′ and ε ′′ with frequency are correlated with various polarisation effects – ionic, dipolar, electronic and space charge that appears at multiple levels of material reaction due to short and long-range movement of mobile charges. 33 The real component of dielectric ( ε ′) indicates the ability of the electrical dipoles within the sample to align with the external electric field, whereas imaginary component of dielectric ( ε ′′) indicates the energy dissipation in the compound. The frequency dependence of dielectric constant, ε ′, and tangent loss, tan δ , of the Sr 2 Ni 1− x Zn x TeO 6 compounds between range of 1 Hz to 0.1 MHz at room temperature are shown in Fig.…”

“…Dependency of 3 0 and 3 00 with frequency are correlated with various polarisation effectsionic, dipolar, electronic and space charge that appears at multiple levels of material reaction due to short and longrange movement of mobile charges. 33 The real component of dielectric samples show a trend similar to normal dielectric materials. At a low frequency ($1 Hz), the dielectric values are the highest for all samples because the dipoles within the samples align themselves along the applied electric eld and contribute fully the total polarisation of dielectric.…”

Undoped Sr2MMoO6 Double Perovskite Molybdates (M = Ni, Mg, Fe) as Promising Anode Materials for Solid Oxide Fuel Cells

“…The most widely used method for synthesizing Sr 2 NiMoO 6-δ is sol-gel technology [ 24 , 34 , 39 , 75 , 88 , 89 ]. A crystalline hydrate of ammonium heptamolybdate (NH 4 ) 6 Mo 7 O 24 ·4H 2 O is used as an Mo-containing component; together with Sr(NO 3 ) 2 and Ni(NO 3 ) 2 ∙6H 2 O, this is dissolved in water.…”

“…Discussing the crystal structure of Sr 2 MgMoO 6-δ , the compound can exhibit cubic (Fm3m [ 89 ]), tetragonal (I4/m [ 19 , 72 , 97 , 98 , 106 , 112 , 113 ]), monoclinic (P2 [ 37 ], P21/n [ 77 , 109 ]) or triclinic I-1 [ 101 , 103 , 104 , 108 , 111 ] crystal structures, depending on the synthesis methods. The triclinic structure was proved by neutron diffraction analysis [ 101 ].…”

Sol-Gel Synthesis of Ceria-Zirconia-Based High-Entropy Oxides as High-Promotion Catalysts for the Synthesis of 1,2-Diketones from Aldehyde

“…The high-entropy oxides were synthesized using a modified, aqueous sol-gel citrate route [49,50] previously reported as a successful route for metal oxides' synthesis. The synthetic procedure is shown in Scheme 2 below.…”