Sol−Gel Synthesis of Nanocrystalline Magnesium Fluoride:  Its Use in the Preparation of MgF₂ Films and MgF₂−SiO₂ Composites

Abstract

Thin, protective films of nanocrystalline MgF 2 were formed by spin-coating a sol that contained nanocrystalline MgF 2 , which was formed by the action of HF on a sol prepared from methanolic H 2 O 2 and Mg(OCH 3 ) 2 . These thin films on Si(100) lost fluoride to form MgO when heated at 550 °C. When the films on two such substrates were placed together face to face and heated at 550 °C, rough, abrasion resistant MgF 2 films were obtained. To form composites, nanocrystalline MgF 2 sols were mixed with silicate sols prepared from the acid catalyzed hydrolysis and condensation of tetramethyl orthosilicate (TMOS). X-ray diffraction and TEM analysis of xerogels and films obtained from these biphasic sols indicated nanocrystals of MgF 2 dispersed in an amorphous matrix. On heating, fluoride loss and MgF 2 crystal growth were both greatly retarded in powders and thin films prepared from silicate-MgF 2 sols.

A comparative study of surface acidity in the amorphous, high surface area solids, aluminium fluoride, magnesium fluoride and magnesium fluoride containing iron(III) or aluminium(III) fluorides

“…It has been used mainly therefore as a catalyst support rather than as an acid catalyst [24,25]. Although MgF 2 of small particle size has been prepared using aqueous or aqueous-organic solgel [26] or microwave [27] techniques, the properties of the solids will be rather different than those reported in the present work, where non-aqueous sol-gel conditions have been used for syntheses of the precursors [14]. Crystalline MgF 2 is a useful host for a range of metal trifluorides, M'F 3 , providing the size of the M' cation is not too different from that of Mg 2+ [17].…”

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials

“…One of the first works reported about MgF 2 NCs and SiO 2 -MgF 2 materials prepared by SG as bulk and thin films dates back to 1996 [20]. Mg(OCH 3 ) 2 and HF were used as Mg and F sources, respectively, to obtain MgF 2 sol.…”

Microwave-assisted synthesis of spherical monodispersed magnesium fluoride

“…It is an insulator with a broad band gap. Magnesium fluoride is used extensively in optical thin films [19][20][21][22][23], for example, as anti-reflective coatings on glasses and as rutile seed for pigment applications [24] and for composite optical filters with titania [25]. It was also reported that magnesium fluoride, which played the role of a support for a number of oxide [26,27], metallic [28] and sulfide [29] phases, enabled syntheses of catalysts active for such reactions as decomposition and reduction of nitrogen oxides [30], hydrodechlorination of chlorofluorocarbons (CFC) [31] and hydrodesulfurization of thiophene [32,33].…”