Low Fluorine Content Research Articles

Chemical vapor synthesis of fluorine-doped SnO2 (FTO) nanoparticles

The synthesis and properties of nanocrystalline SnO2 particles and the effects of doping with fluorine are reported in this work. Simultaneous thermal decomposition of tetramethyltin and difluoromethane in the chemical vapor synthesis process was employed. The nanoparticles were analyzed with respect to their structure using X-ray diffraction followed by Rietveld refinement, transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectroscopy, and Fourier-transformed infrared spectroscopy. Based on the experimental results, a point defect model is proposed, which is supported by density functional theory calculations. At low fluorine concentrations, fluorine substitutes oxygen on a lattice site, while fluorine is located interstitially at high concentrations. The formation of an associated fluorine substitutional–interstitial pair is observed instead of isolated interstitial fluorine.

In vitro cellular adhesion and antimicrobial property of SiO2–MgO–Al2O3–K2O–B2O3–F glass ceramic

The aim of the present study was to examine the cellular functionality and antimicrobial properties of SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics (GC) containing fluorophlogopite as major crystalline phase. The cellular morphology and cell adhesion study using human osteoblast-like Saos-2 cells and mouse fibroblast L929 cells reveals good in vitro cytocompatibility of GC. The potential use of the GC for biomedical application was also assessed by in vitro synthesis of the alkaline phosphatase (ALP) activity of Saos-2 cells. It is proposed that B(2)O(3) actively enhances the cell adhesion and supports osteoconduction process, whereas, fluorine component significantly influences cell viability. The Saos-2 and L929 cells on GC shows extensive multidirectional network of actin cytoskeleton. The in vitro results of this study illustrate how small variation in fluorine and boron in base glass composition influences significantly the biocompatibility and antimicrobial bactericidal property, as evaluated using a range of biochemical assays. Importantly, it shows that the cell viability and osteoconduction can be promoted in glass ceramics with lower fluorine content. The underlying reasons for difference in biological properties are analyzed and reported. It is suggested that oriented crystalline morphology in the lowest fluorine containing glass ceramic enhanced cellular spreading. Overall, the in vitro cell adhesion, cell flattening, cytocompatibility and antimicrobial study of the three different compositions of glass ceramic clearly reveals that microstructure and base glass composition play an important role in enhancing the cellular functionality and antimicrobial property.

Estudio mineralógico, microtermométrico y aspectos estructurales de la mineralización de topacio imperial de Antônio Pereira, Distrito de Ouro Preto (Minas Gerais) - Brasil

Las ocurrencias de topacio imperial de la mina de Antônio Pereira, Ouro Preto, MG, están asociadas a rocas carbonáticas metamórficas del Supergrupo Minas. La densidad del topacio varió desde 3,46 hasta 3,58. Los parámetros de celda unitaria son: 4,658 a 4,663Å (a o), 8,823 a 8,832Å (b o), 8,382 a 8,389Å (c o) y 344,65 a 345,46ų (V). Los índices de refracción son: 1,622 a 1,630 (nX), 1,624 a 1,632 (nY), 1,633 a 1,640 (nZ) y 0,008 a 0,011 (B). Esas propiedades están coherentes con los bajos tenores de flúor obtenidos (16,48%/17,05% en peso). La espectroscopia en el infrarrojo y la microtermometría mostraron que las inclusiones fluidas representativas de los fluidos mineralizantes son formadas por H2O (con Ca2+, Mg2+ y Na+) y CO2 ± CH4. Las condiciones mínimas de atrapamiento de las inclusiones primarias fueron de 290/320oC y 2.349/2.497bar. Las inclusiones pseudosecundarias fueron aprisionadas en menores temperaturas, con presiones variables,, sugiriendo atrapamiento durante procesos de deformación que presentan alternancia local en las condiciones de compresión. La microtermometria conjuntamente con los análisis estructurales y los tenores de flúor indicaron que las vetas con topacio fueron formadas a partir de fluidos hidrotermales originados durante el evento tectónico-metamórfico de edad Brasiliana.

Surface Depletion of the Fluorine Content of Electrospun Fibers of Fluorinated Polyurethane

For materials containing fluorine, it has been generally accepted that fluorinated segments or end groups tend to aggregate in the outer surface because of the low surface energy, which endows the fluorinated materials with special surface properties such as self-cleaning, superhydrophobicity, and so forth. However, for the electrospun fibrous membranes of polyurethane elastomers containing perfluoropolyether segments (FPU), abnormal fluorine aggregations in the core of the electrospun fibers were observed. The XPS analysis indicated a rather low fluorine content at the surface of the electrospun FPU fibers. Further study with dynamic light scattering and fluorescence showed that FPU chains can form aggregates in the concentrated solution. Therefore, it can be deduced that the rapid evaporation of solvent and fast formation of fibers during the electrospinning process could result in the freeze-in of the aggregated chain conformation and the depletion of fluorine units on the surface of the electrospun FPU fibers.

Effects of fluorine doping on the electrochemical properties of LiV 3O 8 cathode material

A series of fluorine-doped lithium trivanadates LiV 3O 8− y F z ( z = 0, 0.03, 0.05, 0.1, 0.15, 0.2 and 0.5) were synthesized by the solid-state reaction. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope (SEM) tests show that a proper amount of fluorine substituting for oxygen in LiV 3O 8 can modify its structure and surface morphology. Charge–discharge tests show that the doped samples with a proper amount of fluorine display good cycling stability, high coulombic efficiency and good rate capability, compared with undoped sample. The cyclic voltammetry (CV), area-specific impedance (ASI) and electrochemical impedance spectroscopy (EIS) tests indicate that the doped samples with a low fluorine content can stabilize the interface between the surface layer of the active particles and the electrolyte after cycling, while a high fluorine content form an unstable interface. The fluorine substitution is a convenient and effective method for improving the electrochemical performances of LiV 3O 8.

The properties of fluorine containing diamond-like carbon films prepared by plasma-enhanced chemical vapour deposition

Films of diamond-like carbon containing up to 39.2 at.% fluorine (F-DLC) were deposited on silicon substrates by radio frequency plasma-enhanced chemical vapour deposition (rf PECVD). A mixture of acetylene (C 2H 2) and carbon tetrafluoride (CF 4) was used for the deposition of F-DLC films. The influence of fluorine content on self-bias voltage, deposition rate, and composition, bonding structure, surface energy, hardness, stress and surface roughness were investigated and correlated with fluorine content. The deposition rate was found to decrease linearly with increasing CF 4 in the plasma due to the higher density of F +. X-ray photoelectron spectroscopy (XPS) analysis revealed the presence C–C, C–CF and C–F for F-DLC films with low fluorine concentration (6.5 at.%), however for films with higher fluorine content (20.7 at.% and 39.2 at.%) an additional peak due to CF 2 bonding was detected. The Raman G-band peak position shifted to higher frequency and can be attributed to the increased amount of sp 2 bonds. Ion scattering spectrometry (ISS) measurements revealed the presence of fluorine atoms in the outmost layer of the F-DLC films and there was no evidence of surface oxygen contamination. The surface energy was found to reduce with increasing fluorine content and has been attributed to the change of the bonding nature in the films, in particularly increasing CF and CF 2 bonds. The addition of fluorine into the DLC film resulted in lower stress and hardness values. The work of adhesion of the surface of the films for Pseudomonas aeruginosa bacteria was estimated to increase with fluorine content, which is indicative of an improved antibacterial activity for F-DLC films.

Properties of fluorine doped ZnO thin films deposited by magnetron sputtering

Fluorine doped ZnO (FZO) films were deposited on Corning glass by radio frequency (rf) magnetron sputtering of pure ZnO target in CF 4 containing gas mixtures, and the compositional, electrical, optical, and structural properties of the as-grown films as well as the vacuum-annealed films were investigated. The fluorine content in FZO films increased with increasing CF 4 content in sputter gas. FZO films deposited at elevated temperature of 150 °C had considerably lower fluorine content and showed a poorer electrical properties than the films deposited at room temperature. Despite high fluorine contents in the films, for all the FZO films, the carrier concentration remained below 2×10 20 cm −3, leading to fairly low doping efficiency level. Vacuum-annealing of the FZO films deposited at room temperature resulted in substantial increase of Hall mobilities, reaching as high as 43 cm 2/Vs. This was attributed partly to the removing of oxygen vacancies and/or the forming chemical bonds with interstitial zinc atoms by fluorine interstitials and partly to the passivation effect of excess fluorine atoms by filling in the dangling bonds at the grain boundaries. For all the films with thickness of around 300 nm, the optical transmissions in visible were higher than 80%, and increased with increasing fluorine content up to 85% for the film with highest fluorine content.

Properties of fluorine-doped PbMg1/3Nb2/3O3 ceramics

We report the first fluorine doping of lead magnesium niobate in the PbMg (1 + x)/3Nb(2 − x)/3O3 − x F x system in a wide composition range, x = 0.025 to 0.625. The fluorine content of the samples is shown to be substantially lower than the intended one because of the fluorine volatilization in the form of HF during synthesis and sintering in air. The ceramics consist of magnesium and lead oxides undetectable by x-ray diffraction, and a perovskite phase whose composition can be represented by the formula PbMg(1 + m)/3Nb(2 − m)/3O3 − m F m , where the fluorine content after sintering is m ≤ 0.12. The PbO and MgO contents of the ceramics depend on the starting mixture composition (x) and heat-treatment conditions (hydrogen fluoride and lead oxide volatilization). As a result of the low fluorine content, the diffraction patterns of the samples show no superlattice reflections, and their lattice parameter varies insignificantly with x. Data are presented on the temperaturedependent dielectric permittivity of ceramic samples sintered and annealed under different conditions.

Fluid components in accessory minerals of Pan-African granitoids in the Sør Rondane Mountains, East Antarctica

Fluids (fluorine, chlorine, and OH) in accessory minerals (apatite, titanite and allanite) of Pan-African granitoids (Group-I granitoids, Group-II granitoids and Mefjell Plutonic Complex) from the Sor Rondane Mountains, East Antarctica were precisely measured by an electronic microprobe analyzer in this study. Apatites in the granites have commonly high fluorine contents. However, fluorine contents from the Group-I, Group-II granitoids and Mefjell Plutonic Complex (MPC) are of important variation, which F contents (3.21∼7.20 wt%) in apatite from the Group-II granitoids are much higher than those from the Group-I granitoids (1.22∼3.60 wt%) and the MPC (3.21∼4.11 wt%). Titanite in the MPC has a low fluorine content (0.23∼0.50 wt%), being less than those in the Group-I granitoids (2.28 wt%) and Group-II granitoids (1.85∼2.78 wt%). Fluorine in allanite in the Group-II granitoids seems to have much lower contents than those from the Group-I granitoids and the MPC. Higher fluorine contents in the titanite from the Group-II granitoids may be mainly controlled by late-magmatic fluid-rock interaction processes associated with melt, but may not be indicative of original magma contents based on its petrographic feature. Due to very lower chlorine contents from all of accessory minerals, the authors suggest that titanite and apatite with higher fluorine contents in the Group-II granitoids have much lower H2O (OH) contents compared with those in the Group-I granitoids according to the partition among (F, Cl, OH). Fluorine contents in whole-rock samples show a variation from the higher in the Group-I granitoids to the lower in the Group-II granitoids and the MPC, which are consistent with the changes of those from the biotite and hornblende as well as fluorite occurred in the Group-I granitoids reported previously. Based on the above study of fluorine in accessory minerals and combined with the previous fluorine contents from biotites and hornblendes, the authors suggest that apatites and titanites with higher F contents in the Group-II granitoids and the MPC may not be an indicator of higher fluorine contents in whole-rock, which reflect fluorine contents in magma sources and/or late-thermal activity. Higher fluorine contents in apatite, titanite and allanite may be an additional evidence of A-type affinity.

Fluorinated Acrylic Films: Effect of F Content on Aging and Corrosion Testing

Four fluorinated polyacrylate dispersions, which based on chlorotrifluoroethylene (CTFE), acrylic acid (AA), vinyl acetate (VAc) and ethenyltriethoxysilane (ETOS) as monomers, are synthesized by free radical polymerization. The influence of xenon lamp and UV-light aging on the film with the fluorine content is discussed. The effect of salt-spray corrosion before and after UV-light aging with F wt% of film is also studied. The results show that low surface energy of high fluorine content film can retard salt-spray corrosion compared with no or low fluorine content films.

Creating Stable Hydrophobic Surfaces by Poly(butyl methacrylate) End-Capped with 2-perfluorooctylethyl Methacrylate Units

It is a challenge to fabricate fluorine-containing polymer surface with low-energy properties and superior long-lasting barrier properties as well as lower fluorine content. In this paper, poly(butyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate units (PBMA-ec-FMA) , having the so-called push-me/pull-you structures, have been synthesized by ATRP and their surface properties were investigated. This structure was in favorable of the longer -(CF2)7CF3moieties self-assembling on the polymer surface during film formation, which resulted in better chain alignment and packing of the longer -(CF2)7CF3moieties. Therefore, the contact angles of water and paraffin oil on the surface of the end-capped PBMA were 118° and 84°, respectively, approaching that of poly(2-perfluorooctylethyl methacrylate) homopolymer, even though the content of FMA was 0.34 mol% (the average polymerization degree of PFMA units is 1). However, more than 9 mol% was necessary for the relative random copolymer (PBMA-r-PFMA) to reach these values of the contact angle. Regardless of the wetting properties, the end-capped PBMA by fluorinated methacrylate has better resistance to surface reconstruction than PBMA-r-PFMA random copolymer even though FMA content in PBMA-ec-FMA is much lower than that in random copolymer. Therefore, it may be a facile method to create stable hydrophobic surfaces with lower price.

Liquidus Equilibria in the System K2O-Na2O-Al2O3-SiO2-F2O-1-H2O to 100 MPa: II. Differentiation Paths of Fluorosilicic Magmas in Hydrous Systems

We investigated phase equilibria in the six-component system Na2O^K2O^Al2O3^SiO2^F2O 1^H2O at 100MPa to characterize differentiation paths of natural fluorine-bearing granitic and rhyolitic magmas. Topaz and cryolite are stable saturating solid phases in calcium-poor systems. At 100MPa the maximum solidus depression and fluorine solubility in evolving silicic melts are controlled by the eutectics haplogranite^cryolite^H2O at 6408C and 4 wt% F, and haplogranite^topaz^H2O at 6408C and 2 wt% F.Topaz and cryolite form a binary peralkaline eutectic at 6608C, 100MPa and fluid saturation.The low-temperature nature of this invariant point causes displacement of multiphase eutectics with quartz and alkali feldspar towards the topaz^cryolite join and enables the silicate liquidus and cotectic surfaces to extend to very high fluorine concentrations (more than 30 wt % F) for weakly peraluminous and subaluminous compositions. The differentiation of fluorine-bearing magmas follows two distinct paths of fluorine behavior, depending on whether additional minerals buffer the alkali/alumina ratio in the melt. In systems with micas or aluminosilicates that buffer the activity of alumina, magmatic crystallization will reach either topaz or cryolite saturation and the system solidifies at low fluorine concentration. In leucogranitic suites precipitating quartz and feldspar only, the liquid line of descent will reach topaz or cryolite but fluorine will continue to increase until the quaternary eutectic with two fluorine-bearing solid phases is reached at 5408C, 100MPa and aqueous-fluid saturation. The maximum water solubility in the haplogranitic melts increases with the fluorine content and reaches 12 5 0 5 wt % H2Oat the quartz^cryolite^ topaz eutectic composition. A continuous transition between hydrous fluorosilicate melts and solute-rich aqueous fluids is not documented by this study. Our experimental results are applicable to leucocratic fluorosilicic magmas. In multicomponent systems, however, the presence of calcium may severely limit enrichment of fluorine by crystallization of fluorite.

Promoting effect of fluorine on titania-supported cobalt–molybdenum hydrodesulfurization catalysts

Abstract The species of a series of F–TiO2 support containing various amounts of fluorine (0–4.30 wt.%) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), and pyridine-adsorbed IR. The results show that the addition of fluorine has a large effect on titania support and two kinds of fluorides are found to be formed in titania support after titania support is treated by NH4F. The state of the fluoride depends on the fluorine content. With lower fluorine content (≤0.94 wt.%) only one kind of fluoride is formed. Further increase in the fluorine content (≥2.07 wt.%) results in the formation of two kinds of fluorides. ESR analysis confirmed the formation of Ti3+ species after fluorine-modification, which actually exists as Ti4+ species containing an oxygen vacancy with an electron trapped in. Co–Mo catalysts supported on fluorine-modified titania presented higher HDS activities than Co–Mo catalyst supported on untreated titania. The hydrodesulfurization mechanism on sulfided fluorine-promoted cobalt–molybdenum/titania catalysts was discussed in this report.

Composition and morphological characteristics of chemically sprayed fluorine-doped zinc oxide thin films deposited on Si(1 0 0)

Fluorine-doped zinc oxide thin films (ZnO:F) were deposited on Si(1 0 0) substrates by the chemical spray technique (CST) from an aged-solution. The effect of the substrate temperature on the morphology and composition of the ZnO:F thin films was studied. The films were polycrystalline, with a preferential growth along the ZnO (0 0 2) plane, irrespective of the deposition temperature. The average crystal size within the films was ca. 35 nm and the morphology of the surface was found to be dependent on the substrate temperature. At low substrate temperatures irregular-shaped grains were observed, whereas at higher temperatures uniform flat grains were obtained. Elemental analysis showed that the composition of the films is close to stoichiometric ZnO and that samples contain quite a low fluorine concentration, which decreases as a function of the deposition temperature.

Surface kinetics modeling of silicon and silicon oxide plasma etching. I. Effect of neutral and ion fluxes on etching yield of silicon oxide in fluorocarbon plasmas

Silicon oxide etching processes in C2F6 and C4F8+80% Ar plasmas were investigated. Neutral and ion compositions in the plasma were measured using quadrupole mass spectrometry and etching yield was measured by a quartz-crystal microbalance. In C2F6 plasma, the concentration of atomic fluorine in the neutral flux was 5%–25%, whereas there was less than 0.5% of atomic fluorine in C4F8+80% Ar plasma. A surface plot representing the etching yield as a function of neutral and ion fluxes was constructed and used to qualitatively explain the etching characteristics of silicon oxide in fluorocarbon plasmas. In C2F6 chemistry, etching yield decreases slightly with increasing rf coil power. This is attributed to the decrease in both F/ion and CFx/ion, which is caused by an increase in ion flux, with a more significant effect due to a decrease in F/ion. In C4F8+80% Ar chemistry, however, etching yield increases with increasing rf coil power. This is attributed to the decrease in CFx, without the effect of F/ion due to the low atomic fluorine concentration. With increased operating pressure, etching yield decreases for both chemistries because as the pressure increases, ion current decreases, and CFx neutral concentration increases to have more deposition and less etching.

The pink topaz-bearing calcite, quartz, white mica veins from Ghundao Hill (North West Frontier Province, Pakistan): K/Ar age, stable isotope and REE data

In the area of the Ghundao Hill (Northern Frontier Province, Pakistan) an orange-yellow to cherry-red topaz is found in calcite, quartz, white mica veins crosscutting the schistosity of probably Silurian to Devonian gray limestones. Topaz with such a range of colours is traded as Imperial Topaz. Low fluorine contents of about 15 wt.%, oxygen isotope thermometry, K/Ar age determination on white mica, fluid inclusion data and mineral textures indicate that the topaz from Ghundao Hill crystallized at temperatures of about 230 °C during the Eocene Himalayan tectonothermal event and not from a late to postmagmatic granite-related fluid. The pink Topaz from Ghundao Hill shares the coexistence with carbonates, low fluorine content and a crystallization at low temperature and pressure during a regional tectonothermal event with the Imperial Topaz from Ouro Preto (Brazil) and from the Sanarka/Kamenka rivers (South Urals, Russia). The efficiency of topaz to remove fluorine from fluids at low temperature explains how topaz can be formed from metamorphic fluids that are typically poor in fluorine. High CO2 activity produced in the fluids by metamorphic decarbonatisation reactions and Al buffering by white mica prevented fluorination of carbonates stabilising topaz relative to fluorite.

Fluorine, chlorine and sulphur emissions from the Andalusian ceramic industry (Spain)—Proposal for their reduction and estimation of threshold emission values

The aims of this paper are concerned with the evaluation of F, Cl and S emissions, originated from the raw material used in Andalusian ceramic factories, which are affected by the European directive. Forty-one ceramic factories were sampled corresponding to the most important production centres in Andalusia, with production rate ranging from 30 to 400 t/day. One hundred and sixty-three samples were studied, including raw materials, extrusion moulded samples, and fire products. Concerning fluorine emission, the lower values (<208 ppm) correspond to materials with low fluorine contents and/or high carbonate content, and firing temperature ≤850 °C. High fluorine emission (208–399 ppm) occurs when initial fluorine contents are high and/or the firing temperature exceeds 900 °C, or well carbonates are lacking. Problematic values higher than the 90th percentile (389 ppm) are usually when the temperature control is not efficient (Hoffman kiln) and exceeds 850 °C. Chlorine emissions are directly related to its content in the raw material. Factories exceeding the emission 90th percentile (1141 ppm) work with raw material containing halite and low percentage of illite, being fired at temperature around 850C. Sulphur emissions will happen only when raw materials of high sulphur contents (>4600 ppm) and low calcite percentage (<15%) are used because if firing temperature is ≥850 °C the CaO can react with SO2 and form efflorescence of gypsum/anhydrite on the fired product.The following measures can be implemented in order to diminish the F emission rates: (a) an accurate temperature control, not exceeding a maximum firing temperature of 850 °C (tunnel kiln is highly recommended); (b) fix fluorine by means of common carbonates if the content in the raw material is <10%; (c) use, alternatively, loams with lesser F contents, if it is possible; (d) for special products fired at higher temperatures (∼1000 °C) solution should be focussed on installing filters in the kiln's chimneys because F emission would usually be high. Finally, to avoid chlorine emissions, raw materials without halite should be used, and if the original loam contains S, emissions can be controlled by calcite content (or additions).

Effect of fluorine content on mechanical properties of sintered fluoridated hydroxyapatite

The effect of fluorine content, preparing method, and sintering temperature on both the bulk density and biaxial flexural strength of sintered fluoridated hydroxyapatite (FHA) was studied. Both uniaxially pressed un-milled (UPU) and cold isostatically pressed milled (IPM) FHA discs were sintered at temperatures between 1200∼1400 °C at an interval of 100 °C. It was found that the fluorine content had significant impact on the sintering behavior, densification, and mechanical properties of FHA discs. At a low fluorine content, the specimens decomposed between 1200–1400 °C, which resulted in a relatively low sintered density and biaxial flexural strength of the specimens. In comparison, the specimens with high fluorine content did not decompose even at the sintering temperature of 1400 °C. The sintered density and biaxial flexural strength of these specimens increased with the sintering temperature. The maximum sintered density and biaxial flexural strength of the UPU specimens were only 85% of the theoretical density and 45 MPa, respectively. In contrast, much higher sintered density (∼95% of the theoretical density) and mechanical strength (∼100 MPa) were attained for the specimens subjected to the cold isostatic pressing and ball milling. A close correlation between the sintered density and biaxial flexural strength of the specimens was revealed, where the biaxial flexural strength increased exponentially with the sintered density.

Structural and electrochemical properties of LiNi 1/3Mn 1/3Co 1/3O 2− xF x prepared by solid state reaction

A series of LiNi 1/3Mn 1/3Co 1/3O 2− x F x (0 ≤ x ≤ 1) compounds was prepared by a solid state reaction and their characteristics were investigated by XRD, SEM, XPS, EIS, and charge–discharge test. The substitution of oxygen by fluorine produces change in the valences of the transition metal ions, thereby induces a complex change in the lattice parameters. Moreover, the fluorine doping of the LiNi 1/3Mn 1/3Co 1/3O 2 can promote the grain size growth and improve its crystallinity. The substituted samples with a low fluorine content can stabilize the interface between the surface layer of the active particles and the electrolyte after cycling, which is probably related to the improvement of the cyclic performance. A high fluorine content introduction into LiNi 1/3Mn 1/3Co 1/3O 2 significantly decreases its electrochemical properties, which is probably due to the formation of a new unstable interface as well as a structural instability caused by the nonequivilent substitution.

Crystallisation in apatite-mullite glass–ceramics as a function of fluorine content

Apatite-mullite glass–ceramics are materials prepared by the controlled heat-induced devitrification of glasses of suitable composition and are under investigation for applications in dentistry and orthopaedics. The glasses used here are based on a system with the composition 1.5(5− x)SiO 2·(5− x)Al 2O 3·1.5P 2O 5·(5− x)CaO· xCaF 2. The amount of fluorine in the glasses was varied to investigate the crystallisation behaviour as a function of both fluorine content and temperature. The resultant crystalline phases are fluorapatite [Ca 10(PO 4) 6F 2], mullite [Al 6Si 2O 13] and in some cases, anorthite [CaAl 2Si 2O 8]. Crystal phases were identified using X-ray diffraction (XRD) from both the surface and the bulk of heat-treated monolithic samples and scanning electron microscopy (SEM) was used to image the crystal phase morphologies. Crystallisation characteristics varied widely in terms of apparent nucleation mechanism, crystal phases formed and microstructure. In general, glasses with higher fluorine content devitrified more readily to fluorapatite (FAp) with a higher nucleation density and for glasses with an intermediate to low fluorine content there tended to be an interdependence between FAp and mullite crystallisation. A greater tendency towards anorthite formation, especially at surfaces, was observed for glasses with lower fluorine contents. Furthermore, on decreasing the fluorine content, glasses tended to crystallise by formation of FAp spherulites with increasing diameter and with greater crystal aspect ratio.