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Solar Water-Splitting
Published in Anirban Das, Gyandshwar Kumar Rao, Kasinath Ojha, Photoelectrochemical Generation of Fuels, 2023
Laxmikanta Mallick, Mrinal Kanti Adak, Priyam Guha, Biswarup Chakraborty
Binary transition metal oxides with spinel structure show promising functional properties in chemical sensors, electrocatalysis, and energy storage applications.99 Crystallographically, spinels are two types normal spinels and inverse spinels. The general elemental formula of normal spinel is AB2X4, where A and B are divalent and trivalent cations, respectively, X is a chalcogenide or oxide. In inverse spinel, a cation occupies an octahedral position, while half of the B cation occupies a tetrahedral position. Normal and inverse spinel is represented by (AII)tet(BIII)2octO4 and (BIII)tet(AIIBIII)octO4, respectively.100
Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Figure 3.25 shows the atomic arrangement in spinel. The drawing on the right, with the atoms removed, emphasizes the fact that the arrangement is cubic. Mineralogists often group minerals that have the same basic atomic arrangements, even if they have different compositions. Sometimes, the group name is the same as one of the individual mineral species, adding some confusion. The mineral spinel, for example, has the specific composition MgAl2O4. The spinel group, however, consists of more than a dozen minerals, all with the general formula AB2O4. The A elements include Fe, Zn, Mn, Mg, or Ni; the B elements include Cr, Al, Fe, or Ti. No matter the elements present, the A atoms are bonded to four oxygen atoms, and the B atoms are bonded to six oxygen atoms. Angles between bonds and crystal shape are the same for all spinel group minerals, giving an overall cube-shaped structure, and the overall atomic arrangement is as shown in this figure.
Spinel Ferrites—A Future Boon to Nanotechnology- Based Therapies
Published in Nandakumar Kalarikkal, Sabu Thomas, Obey Koshy, Nanomaterials, 2018
R Sharath, Nagaraju Kottam, H Muktha, K Samrat, M. Chandraprabha, R Harikrishna, Bincy Rose Vergis
Ferrites are chemical compounds with the formula of AB2O4, where A and B represent various metal cations; usually including iron. Ferrites are considered a class of spinels that consist of cubic closed pack oxides with a cation occupying one-eighth of the octahedral voids and B cations occupying half of the octahedral voids. For the inverse spinel structure, half the B cations occupy tetrahedral sites and both the A and B cations occupy the octahedral sites. Meanwhile, divalent, trivalent, and quadrivalent cations can occupy the A and B sites and they include Mg, Zn, Fe, Mn, Al, Cr, Ti, and Si. Ferrites are ferromagnetic ceramic compounds usually non-conductive derived from iron oxides as well as oxides of other metals. Like most other ceramics, ferrites are hard and brittle. Ferrites are manufactured by homogeneously mixing iron oxides and then calcinating the mixture which causes the partial decomposition of carbonates and oxides. This mixture is then sintered which is done by gradually raising the temperature to 1500°C in a klin. Typically, the cores will shrink by 10-20% of its original size after sintering. The mixture crystallizes into cubic structure; the resulting ferrite has a black nonporous ceramic appearance. Ferrites are often classified as soft ferrites and hard ferrites, which is based on their ability to be magnetized or demagnetized and can also be classified based on their coercive field strength. Soft ferrites can be easily magnetized and demagnetized thus making them to be used as electromagnets they have low coercive field strength, while hard ferrites are used as permanent magnets and have high coercive field strength. Ferrites are widely used in high-frequency applications because an alternating current (AC) field does not induce undesirable eddy currents in an insulating material.4
Origin and evolution of nephrites, diopsidites and giant diopside crystals from the contact zones of the Pounamu Ultramafics, Westland, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Spinel occurs in several rocks as inclusions in diopside, garnet and epidote. It is predominantly Cr-rich, but significantly contains high concentrations of Zn (up to 12.57 wt. % ZnO in OU86921 and 12.13 wt.% ZnO in OU86924) and MnO (2.35–3.99 wt %)(Table 3). Stoichiometric considerations indicate that an ideal oxyspinel formula, AB2O4, results when Fe is exclusively present as Fe2+. Fe dominates the A site and Cr the B site, so the accepted IMA classification (Bosi et al. 2018) is chromite, with Cr# (Cr/(Cr + Al + Fe3+)) of 0.74. The high Zn content indicates a significant (∼25–30 mol %) of the zincochromite component. Similar zincian chromites have been documented by Challis et al. (1995) in metasomatic rocks from north-west Nelson, New Zealand, where they are associated with Cr-muscovite and uvarovite.
Spinel-based electrode materials for application in electrochemical supercapacitors – present status and future prospects
Published in Inorganic and Nano-Metal Chemistry, 2022
Vismaya Jose, Vinaya Jose, Clementz Edwardraj Freeda Christy, Arputharaj Samson Nesaraj
Spinel is the magnesium/aluminium part of the larger group of spinel minerals. The name comes from the Latin word spinella, meaning spine in reference to its pointed crystals.[33] Usually, the common equation for a spinel is AB2O4, where A refers to a divalent metal ion (M2+) and B refers to a trivalent metal ion (M3+). In a typical spinel structure, the A ions involve the tetrahedral sites and the B ions involve the octahedral sites.[34] In inverse spinel, the A particles have octahedral sites, while half of the B particles possess tetrahedral voids and the other half have octahedral sites.[35] Spinel, (Mg,Fe)(Al,Cr)2O4, is common in peridotite within the uppermost mantle of earth and Spinel, (Mg,Fe)Al2O4, may be a common mineral within the Ca-Al-rich considerations (CAIs).[36–38] Synthetic spinel, accidentally delivered within the center of the 18th century. It looks like glass, but its compression resistance is significantly improved. It can also be used in military and commercial applications.[39–41]
Spinel ferrite of MnFe2O4 synthesized in Piper betle Linn extract media and its application as photocatalysts and antibacterial
Published in Journal of Dispersion Science and Technology, 2021
Rahmayeni Rahmayeni, Yenti Oktavia, Yeni Stiadi, Syukri Arief, Zulhadjri Zulhadjri
Magnetic materials are of great interest for both fundamental science and technological applications due to their chemical and physical properties, especially their magnetic properties. Spinel ferrite is a magnetic material that has a narrow band gap (< 2 eV) with the molecular formula AB2O4, where A is a divalent metal ion and B is Fe3+. Spinel ferrite has several spinel structures, including normal, mixed, and inversed spinel. For mixed spinel structures such as MnFe2O4, two sub-lattices at A position (tetrahedral site) and B position (octahedral site) are occupied by Mn2+ and Fe3+ ions.[1,2] Recently, spinel ferrite has attracted the attention of researchers and has been widely developed due to its wide and potential applications such as data storage, biosensors, pharmaceutical delivery, disease diagnosis, hyperthermia, gas sensors, electronic devices, energy conversion, magnetic fluid, photocatalysts, antibacterial, and electro communication.[3–7]