Size reduction-induced properties modifications of antiferromagnetic dielectric nanocrystalline Ba2NiMO6 (M = W, Te) double perovskites

Abstract

The main objective of this work was to synthesize phase pure double perovskites Ba2NiTeO6 (BNTO) and Ba2NiWO6 (BNWO) in nanocrystalline form and to reveal the impact of nanocrystallinity onto their magnetic and dielectric properties. The studied double perovskites were synthesized in nanocrystalline form by employing citrate sol-gel route. A detailed investigation of their structure and properties using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy technique, energy-dispersive X-ray spectroscopy (EDS), SQUID magnetometry and electrical measurements is carefully described. Rietveld refinement of XRD patterns revealed phase purity of both compounds, BNTO is trigonal (R-3m) while BNWO is cubic (Fm-3m). Raman spectroscopy studies reveal optical phonons that correspond to vibrations of Te6+/W6+O6 octahedra, while SEM images show irregular plate-like nanocrystals. Magnetic property measurements speak in favor of antiferromagnetic order but in both compounds size reduction affected their properties. BNTO has Néel temperature (TN) of 10.3 K which is higher than previously reported for its bulk form. Magnetic ground state of BNWO can be explained as canted antiferromagnetism with TN = 48.2 K. Room temperature measurements of dielectric constants at various frequencies suggest that these materials are high-κ dielectrics with low dielectric loss. The Nyquist plot reveals depressed semicircle arc typical for non-Debye type of relaxation phenomena for BNWO ceramic, whereas for BNTO ceramic almost straight line of Zʹʹ versus Z’ has been observed indicating its high insulating behavior. To conclude, size-dependent properties of studied double perovskites are discussed introducing a possibility for implementation in electronic devices.

Bandgap Engineering in Novel Fluorite‐Type Rare Earth High‐Entropy Oxides (RE‐HEOs) with Computational and Experimental Validation for Photocatalytic Water Splitting Applications

“…All compounds were synthesized using a modified, ecofriendly and simple aqueous sol-gel citrate route developed previously in the synthesis of high-entropy oxides [47] and double and triple perovskite oxides. [48][49][50][51][52][53] Detailed characterization of the as-synthesized RE-HEOs and performance measurements were executed along with theoretical calculations using density functional theory (DFT) to establish a plausible mechanism for photocatalytic detoxification of MB dye and photoelectrochemical (PEC) water splitting by the high entropy oxides. This study meets United Nation's Sustainable Development Goals toward clean water and sanitation and affordable and clean energy.…”

Nanocrystalline triple perovskite compounds A3Fe2BO9(A = Sr, Ba; B = W, Te) with ferromagnetic and dielectric properties for triboelectric energy harvesting

“…A similar explanation was already proposed for the absence of NiO 6 vibrations in the Raman spectra of Ni-based double perovskites. 24,25…”

“…A Nabertherm LT5/11/B410 furnace was used for calcination. Targeted compounds were synthesized using the aqueous citrate sol-gel route previously reported by our group 17,19,24,25 for obtaining double and triple tungsten-and tellurium-based perovskites. Stoichiometric amounts of Sr 2+ /Ba 2+ (3 mmol), Fe 3+ (2 mmol) and Te 6+ (1 mmol) metal salt precursors were dissolved in 100 mL of citric acid solution (w = 10%).…”

“…This synthesis route is simple, cost-effective, environmentally friendly and it has been proved to be successful in obtaining nanocrystalline oxide powder structures 23 such as double and triple perovskites. 17,19,24,25…”

“…This synthesis route is simple, cost-effective, environmentally friendly and it has been proved to be successful in obtaining nanocrystalline oxide powder structures 23 such as double and triple perovskites. 17,19,24,25 Perovskite structures, both inorganic and hybrid, have been used as components of triboelectric nanogenerators (TENGs) because of their unique electrical properties. [26][27][28][29][30][31] The concept of triboelectric nanogenerators was first developed by Fan et al 32 in 2012, which was a changing point of scientific research.…”