Sol-Gel Preparation and Characterization of Magnesium Peroxide, Magnesium Hydroxide Methoxide, and Randomly and (111) Oriented MgO Thin Films

Abstract

A H202-assisted sol-gel method for the preparation of precursors for formation of thin films of MgO is described. Sols were prepared from the addition of Mg(OCH3)2 to methanolic H2O2. Two such sols, with Mg to H202 ratios of 1:1 and 1:10, were used to prepare, respectively, random or (111) oriented MgO thin films on Si(100). The xerogel from a sol with a 1:10 Mg:H202 ratio contained nanocrystalline Mg02-nH20, whereas the xerogel from a comparable sol with a 1:1 Mg:H202 ratio contained nanocrystals of Mg02,nH20, and Mg-(OH)(OCH3). The latter compound was the hydrolysis product of methanolic Mg(OCH3)2 even when treated with up to 4 equiv of water. The thermal decomposition properties of this compound are reported. Using the published method of treating Mg(N03)2 with excess 30% H202, Mg02-nH20, with a Mg2+:022-ratio of 1:0.74, was prepared. Based on IR, TGA, and DTA results, it is proposed that the material also contained oxide, and possibly hydroxide ions for charge balance. These ions were present either in an amorphous phase, or possibly substituted for 022-in the Mg02 crystal structure.

Ab InitioQuantum Mechanical Study of the Structure and Stability of the Alkaline Earth Metal Oxides and Peroxides

“…Our results suggest that the experimentally reported content of H O/ H O in MgO samples (9,12) is necessary for the stabilization of the compound. Finally, BeO has a huge negative decomposition energy of !129 kJ/mol, which means that it is completely unstable in the pyrite structure, and in view of the magnitude of this term it is certainly not possible, as in the case of MgO , to stabilize the compound with…”

“…3 group Pa3 ), which can also be derived from that of rock salt, by siting the Mg> (Zn> and Cd>) ions at the cation sites, while the O\ groups are again centred around the anion sites and rotated by 45°from the direction of the cubic axes. As for the case of CaO , it has not proved possible to prepare MgO in a pure form, with all samples again containing water and/or hydrogen peroxide from the preparation procedure (9,12). Moreover, the question of whether water and/or hydrogen peroxide is included as part of the crystal structure or only physically adsorbed is not easy to decide partly because only powder data are available for this material (13).…”

Electrical and optical properties of MgO thin film prepared by sol-gel technique

“…A recent paper by Yoon et al disclosed that the (111) oriented MgO film on Si substrate was prepared by spincoating sol-gel method, using magnesium ethoxide as the starting material [23]. Another work by Rywak et al also obtained (111) oriented MgO films by hydrogen peroxide assisted sol-gel method [24]. However, no physical properties of these films were reported.…”

Preparation of monodispersed magnesia coated silica particles through a surface-induced precipitation method

“…The second weight loss observed at 130-220°C is related to the decomposition of the alkoxy group [16]. The third weight loss in the temperature range of 260-380°C is due to the decomposition of magnesium hydroxide leading to crystallization of magnesia and the removal of the organic group in the precursor.…”

“…The absorption band at 550-600 cm −1 originated from the alkoxy group with the shape of the Mg-OR (R is the alkoxy group) stretching mode [21]. The sharp adsorption peak at 3700 cm −1 is attributed to hydroxide ions in the magnesium hydroxide coating layer, which is formed from the hydrolysis of Mgalkoxide with water through the precipitation coating system [16,22]. After calcination of the magnesium hydroxide at 700°C (curve (c)), the Mg-O stretching mode at 550-600 cm −1 is flattened.…”