Fluorolytic Sol–Gel Synthesis of Nanometal Fluorides: Accessing New Materials for Optical Applications

Abstract

The potential of fluorolytic sol–gel synthesis for a wide variety of applications in the field of optical materials is reviewed. Based on the fluorolytic sol–gel synthesis of nanometal fluorides, sols of complex fluorometalates have become available that exhibit superior optical properties over known classical binary metal fluorides as, for instance, magnesium fluoride, calcium fluoride, or strontium fluoride, respectively. The synthesis of transparent sols of magnesium fluoroaluminates of the general composition MgxAlFy, and fluoroperovskites, [K1−xNax]MgF3, is reported. Antireflective coatings fabricated from MgF2, CaF2, MgxAlFy, and [K1−xNax]MgF3 sols and their relevant properties are comprehensively described. Especially the heavier alkaline earth metal fluorides and the fluorperovskites crystallizing in a cubic crystal structure are excellent hosts for rare earth (RE) metals. Thus, the second chapter reflects the synthesis approach and the properties of luminescent systems based on RE-doped alkaline earth metal fluorides and [K1−xNax]MgF3 phases.

Synthesis of pure and doped nano-calcium phosphates using different conventional methods for biomedical applications: a review

“…9,177 Many different types of materials such as nanoporous oxides, nanoscale architectures, including nanomaterials, nanocoating, organic–inorganic hybrids, monolithic structures, metal–organic frameworks, bioinspired materials, glasses, and amorphous composites have been prepared using a conventional sol–gel method for a few decades. 178–228 The sol–gel method was employed to successfully produce nanosized HAp particles and effects of doping is given in Table 6. This was achieved by utilizing various calcium and phosphorous precursors, including Ca(OH) 2 , in a solution composed of ethanol and water, as well as phosphoric acid (H 3 PO 4 ), at a pH of 11.…”

Synthesis of KZnF\(_{3}\) Phosphors by Co-Precipitation Method

“…It involves heating of constituent fluorides in H 2 [31] or HF [7] atmosphere at 800 C. To overcome the problems involved in such procedure, various novel techniques have been tried. These include solid-state metathesis, solvothermal [21,29,44,47] microwave method [34], glass ceramics [28], coprecipitation [19,26,46], fluorolytic Sol-Gel Synthesis [35], etc.…”

First Mixed-Metal Fluoride Pyrochlores Obtained by Topotactic Oxidation of Ammonium Fluorides under F2 Gas

“…To overcome such a problem, several strategies have been considered by (i) mixing FeF 3 with conductive carbon compounds (CNT, graphene, OMC, ...), − (ii) reducing the particle size, and (iii) reducing the band gap of materials by either substituting F – ions with O 2– /OH – ions or vacancies , or doping FeF 3 with isovalent cations (Ti, Cr, Mn, Co). − Therefore, in order to control the particle size and the fluorination degree, to obtain new cation combinations and to stabilize the metastable polymorphs, numerous synthesis routes have been explored. Mechanochemical synthesis is technically simple and gives high yields; it was successfully applied to prepare nanostructured metal fluorides. , Metal fluorides with a high surface area are obtained in hydrofluoric acid (HF) solutions using solvothermal or sol–gel methods. − In addition, solvothermal syntheses assisted by microwave heating give metastable and novel metal fluoride phases. − Nevertheless, the presence of water during the synthesis often leads to hydrated phases and also to frequent F – /OH – substitution, which can be detrimental to catalytic or electrochemical properties.…”