Fluoride promoted crystallization and mechanical properties of Sr-fluorphlogopite glass

Crystallization, microstructure and mechanical behavior of strontium fluorphlogopite glass-ceramics, SrO·4MgO·Al₂O₃·6SiO₂·2MgF₂, was studied by varying the fluorine content. A number of glass-ceramics of each glass batch with excess MgF₂ [SR0 (0% MgF₂), SR5 (5% MgF₂) and SR10 (10% MgF₂)] were prepared by heating at its respective nucleation temperature followed by at different crystallization temperatures (780–1150 °C). Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Micro Hardness Indenter were used to study the crystallization, microstructure and mechanical behavior of resulting three glass batches. DTA analysis revealed that the peak crystallization (T_p) and glass transition (T_g) temperatures decreased with increasing fluorine content that also lowers down the activation energy (E) as evident from crystallization kinetics. Hardness and fracture toughness values are higher for less fluorine containing glass-ceramics when they are treated isothermally. However, more fluorine based glass-ceramics is found to be more machinable than the less fluorine one.     

Dispersion at Single Unit TiO2 Nanoparticles Reduced Tg,Induced Chain Disentanglement and Reduced Tensile Modulus in Waterborne Acrylic Coatings

Spatially distributed TiO₂ nanoparticles induced an order of magnitude decrease of glass transition temperature, T_g, and chain disentanglement in waterborne acrylic coatings. Acrylic/TiO₂ coatings are synthesized in situ by batch emulsion polymerization. The copolymer is based on butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) with composition 56:42:2 mol%, and nano-TiO₂ (ca. 12 nm) is incorporated up to 3 wt% content. Transmission electron microscopy (TEM) showed that TiO₂ is dispersed at nearly single unit throughout the acrylic matrix. The nanoparticle reduced T_g and broadened the temperature range of the glass transition, δT_g. The considerable increase of δT_g suggests gradients of dynamics. Shear rheometry demonstrated that TiO₂ induced chain disentanglement, the rubbery modulus G_e decreased two orders of magnitude with only 1 wt% TiO₂ content thus increasing the packing length p (and the reptation tube diameter as d_t = kp, k > 1). Consequently, the tensile Young's modulus E decreased an order of magnitude, relative to the neat copolymer. The reduction of T_g, the slowdown of macromolecular dynamics, the chain disentanglement and the increase of d_t suggests dynamics modification due to intercalation of the entangled web by the TiO₂ nanoparticles, and these results may be ascribed to a nanoconfinement effect.     

Structural and Textural Modifications of Ternary Phosphate Glasses by Thermal Treatment

Phosphate-based glasses of composition xNa₂O−(45+(10−x))CaO−45P₂O₅ with different Na₂O, CaO (x = 1, 5, 10, 15, and 20 mol%), and invariable P₂O₅ (45 mol%) contents were prepared using the rapid melt quench technique. The obtained thermal data from differential thermal analysis revealed a decline in glass transition (T_g) and crystallization (T_c) temperatures of glasses against the compositional changes. The inclusion of Na₂O at the cost of CaO in the glass network led to a reduction in its thermal stability. The thermal treatment carried out on glasses helped to derive their glass-ceramic counterparts. The amorphous and crystalline features of samples were characterized using X-ray diffraction patterns. The crystalline species that emerged out of the calcium phosphate phases confirmed the dominance of Q¹ and Q² structural distributions in the investigated glass-ceramics. The obtained scanning electron micrographs and atomic force microscopic images confirmed the surface crystallization and textural modification of the samples after thermal treatment. The N₂-adsorption–desorption studies explored the reduction of porous structures due to thermal treatment on the melt-driven glass surface. The measured elastic moduli and Vicker's hardness values of the glasses showed an increase after thermal treatment, which were reduced against the inclusion of alkali content in both glass and glass-ceramics.     

Structure-Property Correlation in BaO-TiO2-B2O3 Glasses: Glass Stability,Optical, Hydrophobic,and Dielectric Properties

Glasses in the x(BaO-TiO₂)-B₂O₃ (x = 0.25, 0.5, 0.75, and 1 mol.) system were fabricated via the conventional melt-quenching technique. Thermal stability and glass-forming ability as determined by differential thermal analysis (DTA) were found to increase with increasing BaO–TiO₂ (BT) content. However, there was no noticeable change in the glass transition temperature (T_g). This was attributed to the active participation of TiO₂ in the network formation especially at higher BT contents via the conversion of the TiO₆ structural units into TiO₄ units, which increased the connectivity and resulted in an increase in crystallization temperature. Dielectric and optical properties at room temperature were studied for all the glasses under investigation. Interestingly, these glasses were found to be hydrophobic. The results obtained were correlated with different structural units and their connectivity in the glasses.     

Influence of nucleating agents on crystallization and electrical properties of SiO2–MgO–MgF2–K2O mica glass-ceramics

The effects of adding ZrO₂ and TiO₂ at the expense of MgF₂ on the crystallization, microstructure, mechanical properties, thermal properties and electrical properties of mica glass-ceramics based on the SiO₂–MgO–MgF₂–K₂O system were investigated by the differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and resistivity tester. The electrical properties were discussed emphatically. The results showed that the additions of ZrO₂ and/or TiO₂ at the expense of MgF₂ effectively increase the viscosity, the glass transition temperatures (T_g) and the crystallization temperatures (T_p) of the glasses. The crystallization activation energy (E_c) of the amorphous glasses varied with the nucleating agents was discussed in depth. It was discovered that the nucleating agents had no effect on the crystal phase type but had a certain effect on the crystallinity and microstructure. Tetrasilicic fluoromica and enstatite were precipitated at different crystallization temperatures. Due to the non-stoichiometric ratio of tetrasilicic fluoromica crystal, the prepared glass-ceramics had high dielectric constant (24.4–34.3) and volume resistivity (>2 × 10¹¹ Ω cm) at 25 ^°C, and the dielectric loss was almost zero.     

Microstructure and ion-exchange properties of transparent glass-ceramics containing Zn2TiO4/α-Zn2SiO4 nanocrystals

Transparent glass-ceramics have particular properties compared with their precursor glasses, and have promising potential applications in many fields. Titanium-relative phases are frequently employed as nucleation agents for crystallization of glass-ceramics, and rarely been precipitated as functional nanocrystalline phases in glass-ceramics. In this work, transparent glass-ceramics containing Zn₂TiO₄ and/or α-Zn₂SiO₄ nanocrystals are investigated. It turns out that Vickers hardness of these glass-ceramics increases with the precipitation of Zn₂TiO₄ and α-Zn₂SiO₄ nanocrystals. Despite the blocking effect of nanocrystals precipitated in the glass-ceramics, structural and compositional modification of the residual glass induced by the precipitation of these nanocrystalline phases facilitates the K-Na ion-exchange, leading to the enhanced depth of layer and further improved Vickers hardness of the glass-ceramics.     

The influence of TiO2 content on the properties of glass ceramics: Crystallization,microstructure and hardness

The effects of compositional variation, crystallization behavior, crystalline phases and microstructure formed in the SiO₂3Al₂O₃3CaO (SAC) glass system using various amounts of TiO₂ as nucleating agent were investigated by Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR) techniques. The crystallization kinetics and mechanical properties of SAC glass ceramics were studied using crystallization peak temperature (T_p) of three different glasses as obtained from DTA, the activation energy (E) and Avrami exponent (n) were also determined. The crystallization peak temperature (T_p) and activation energy (E) were found to increase with the increase in TiO₂ content. The major crystalline phases were anorthite and wollastonite along with gehlenite and titanite as the minor crystalline phases present in the glass ceramic system. The studies showed that the three dimensional crystalline structure and the microhardness increased with the increase of TiO₂ content in the glass ceramics system.     

Role of MgO in lowering glass transition temperature and increasing hardness of lithium silicate glass and glass-ceramics

The effect of variation of MgO (1.5, 4.5 and 7.5 mol%) content on glass structure, crystallization behavior, microstructure and mechanical properties in a Li₂O–K₂O–Na₂O–CaO–MgO–ZrO₂–Al₂O₃–P₂O₅–SiO₂ glass system has been reported here. Increased amount of MgO enhanced the participation of Al₂O₃ as a glass network former along with [SiO₄] tetrahedra, reducing the amount of non-bridging oxygen (NBO) and increasing bridging oxygen (BO) amount in glass. The increased BO in glass resulted in a polymerized glass structure which suppressed the crystallization and subsequently increased the crystallization temperature, bulk density, nano hardness, elastic modulus in the glasses as well as the corresponding glass-ceramics. MgO addition caused phase separation in higher MgO (7.5 mol%) containing glass system which resulted in larger crystals. The nano hardness (～10 GPa) and elastic modulus (～127 GPa) values were found to be on a much higher side in 7.5 mol% MgO containing glass-ceramics as compared to lower MgO containing glass-ceramics.     

Effect of different nucleating agent ratios on the crystallization and properties of MAS glass ceramics

The effects of different kinds of nucleating agents on crystallization, microstructure and performances of Magnesium Aluminosilicate (MgO-Al₂O₃-SiO₂, MAS) glass-ceramics which were fabricated by melting method in this study. Also, this paper systematically investigated the mechanism of glass stability, crystallization kinetics and element distribution of MAS glass-ceramics. Herein, we used three kinds of nucleating agents, which was TiO₂, ZrO₂ and composite nucleating agent (TiO₂/ZrO₂). The results showed after the doping of nucleating agent, the content of α-cordierite was increased, the stability and crystallization kinetics of glass was changed, the precipitated crystal phase was finer and more compact. Wherein, the sample with composite nucleating agents (TiO₂, ZrO₂) has the best performance due to the highest contents of α - cordierite, uniform distribution of elements without agglomeration in the crystal phase and the most compact structure, whose Vickers hardness and bending strength can reach 9.70 GPa and 312 MPa, respectively.     

Enhancement of glass-ceramic performance by TiO2 doping: In vitro cell viability,proliferation, and differentiation

A new TiO₂-containing bioactive glass and glass-ceramics based on 50SiO₂-(45-X)CaO-(XTiO₂)-5P₂O₅ system was designed using a sol–gel technique (where X = 5, 7.5 and 10 wt %). The roles of the crystallization behavior and physicochemical characteristics of the designed glass and glass-ceramics which were played in the introduction of TiO₂ substitutions were investigated. Moreover, cell proliferation and differentiation were evaluated against human osteosarcoma cells (Saos-2). The TiO₂/CaO replacements led to the formation of a stronger glass structure and thus increased thermal parameters and the chemical stabilization of the designed materials. The FTIR data confirmed the existence of Ti within the glass and glass-ceramics samples, and no remarkable effect on their chemical integrity was observed. The XRD patterns indicated that calcium-containing minerals, including Ca₂SiO₄,Ca₃(PO₄)₂, Ca(Ti,Si)O₅, CaTiSiO₅, and Ca₁₅(PO₄)₂·(SiO₄)₆ phases were developed as a role of structure/texture under the applied heat-treatment. The results of the cytotoxicity test proved that a safe sample dose is 12–50 μg/ml, at which cell viability is ≥ 85%. The cell differentiation determined by ALP test proved the superiority of glass-ceramics compared with their native glasses. Therefore, the obtained materials could be safely used as novel biocompatible materials for the regeneration of bone tissue.     

Effect of metastable phase on the crystallization and mechanical properties of MgO-Al2O3-SiO2 glass-ceramics without nucleating agents

Glass-ceramics without nucleating agents usually undergo surface crystallization, which deteriorates the overall performance of the products. In this paper, we evaluated the effects of the metastable MgAl₂Si₃O₁₀ crystalline phase on the crystallization behavior of a MgO–Al₂O₃–SiO₂ (MAS) glass without nucleating agents and mechanical properties of the glass-ceramics obtained. The results demonstrated that the precipitation of metastable MgAl₂Si₃O₁₀ crystallites promotes the crystallization mechanism transformed from surface crystallization into volume crystallization with two-dimensional crystal growth. Furthermore, the grain size of MgAl₂Si₃O₁₀ near the surface of the prepared glass-ceramics was larger than that of MgAl₂Si₃O₁₀ inside, which helps to generate compressive stress and improves its mechanical properties. The glass-ceramics containing metastable MgAl₂Si₃O₁₀ phase exhibited an enhanced hardness in the range of 7.6 GPa–9.5 GPa for indentation loads ranging from 2.94 N to 98 N, and indentation size effect behavior was observed in Vickers hardness tests of both MAS glass and glass-ceramics. The load-independent hardness values for MAS glass and glass-ceramics were reliably evaluated by the modified proportional specimen resistance (MPSR) model of 7.1 GPa and 7.6 GPa, respectively, with a high correlation coefficient of more than 0.9999. This work reveals the unexploited potential of the metastable phase in improving the crystallization ability and mechanical properties of glass-ceramics.     

Effect of ZnO on the crystallization behavior and properties of SiO2–CaO–Al2O3–Fe2O3 glass-ceramics prepared from simulated secondary slag after reduction of copper slag

The feasibility of preparing low-cost glass-ceramics from Zn-containing dust and secondary molten slag generated during the carbothermal reduction of copper slag was investigated. Analytical-grade agents, such as ZnO, Fe₂O₃, SiO₂, CaO, and Al₂O₃, were used to simulate the dust and secondary slag. The effect of ZnO content on the crystallization behavior, structure, and mechanical properties of the glass-ceramics was investigated through X-ray diffraction analysis, scanning electron microscopy-energy dispersive spectrometry, differential scanning calorimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results showed that with increased ZnO content from 0 to 6 wt%, the crystallization activation energy of base glass increased from 386.05 to 425.89 kJ/mol. Meanwhile, the average value of the crystal growth index increased from 1.91 to 4.10, and the highest crystallization rate of the glass-ceramics increased from about 1.44 to 23.11 mm³/min. The increased ZnO in glass-ceramics promoted the precipitation of gehlenite, but inhibit the crystallization of anorthite. When the ZnO content was 6 wt%, the comprehensive properties of the glass-ceramics were better; the flexural strength, microhardness, volume density, water absorption rate, and open porosity were 58.67 MPa, 738.35 HV, 2.92 g/cm³, 0.44% and 1.27%, respectively.     

Processing of transparent glass-ceramics by nanocrystallisation of LaF3

Transparent glass-ceramics have been prepared by heat-treating oxyfluoride glasses in the Na₂O–Al₂O₃–SiO₂–LaF₃ system. The nanocrystallisation of LaF₃ was achieved by controlling time and temperature parameters. Glasses and glass-ceramics were characterised by dilatometry, DTA, XRD and TEM. The mean crystal size (<20 nm) and the crystal fraction increase with the temperature of heat treatment, while they reach a maximum at about 20 h at a temperature close to T_g. The crystallisation of phases containing glass modifier elements as well as F anions leads to the increase in the viscosity of the remaining glass matrix. Phase separation occurs in glass-ceramics depending on the glass composition which affects nanocrystallisation.     

Multiwalled carbon nanotubes‐based polypropylene composites: Influence of interfacial interaction on the crystallization behavior of polypropylene

Composites of polypropylene (PP) and multi‐walled carbon nanotubes (MWCNTs) were prepared via melt‐mixing utilizing Li‐salt of 6‐amino heaxanoic acid (Li‐AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene‐g‐maleic anhydride; PP‐g‐MA). Improved interaction between the anhydride group of PP‐g‐MA and the amine functionality of Li‐AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature (T_g) of the PP phase has been observed in these composites as compared to pristine MWCNTs‐based composites. The crystallization temperature (T_c) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating hetero‐nucleating action of MWCNTs. However, T_c value was decreased in the presence of Li‐AHA modified MWCNTs indicating the adsorbed Li‐AHA on the MWCNTs surface. Moreover, T_c value was higher in the presence of Li‐AHA modified MWCNTs with PP‐g‐MA as compared to that of without PP‐g‐MA, suggesting the desorbed Li‐AHA from the MWCNTs surface due to melt‐interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/MWCNTs composites containing Li‐AHA and PP‐g‐MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the “extracted MWCNTs.” POLYM. ENG. SCI., 57:183–196, 2017. © 2016 Society of Plastics Engineers     

Influence of heat treatment temperature on the properties of the lithium disilicate-fluorcanasite glass-ceramics

This study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate-fluorcanasite glass-ceramics and to develop new dental materials. The glasses and glass-ceramics were prepared using CaF₂-SiO₂-CaO-K₂O-Na₂O-Li₂O-Al₂O₃-P₂O₅-based glass system using a conventional melt quenching method followed by a two-stage crystallization process. This two-stage method involves two heating temperature steps: first at a constant temperature (T_S1) of 600°C and second step at varying temperatures (T_S2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass-ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm³, 6.73 GPa, 3.38 MPa.m^1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate-fluorcanasite glass-ceramics.     

Effect of MgO addition on the properties of PbO –TiO2–B2O3 glass and glass–ceramics

Glass samples with composition of (50?X) PbO–X MgO–25 TiO₂–25B₂O₃ (where X=0, 5, 10 and 15 mol%) were prepared using conventional quenching technique. The amorphous nature of glass samples were confirmed by XRD. The glass transition temperature, T_g and crystallization temperature T_c were determined from the DTA. It has been observed that the addition of MgO enhances the T_g. The rise in T_g with MgO content may be attributed to the greater field strength of Mg²⁺ cation (as compared to Pb²⁺) which leads to the formation of stronger bonds. These glass samples were converted to glass–ceramics by following a two-stage heat treatment schedule. It was observed that there was good correlation between the density and CTE results of the glass–ceramics. The XRD results revealed the formation of tetragonal lead titanate as a major crystalline phase in the glass–ceramics. The addition of MgO to the glass contributes to the formation of MgB₄O₇. The dielectric constant for all the glass–ceramic samples was observed to be higher than that of corresponding glass samples. Further, with addition of MgO the room temperature dielectric constant for glass–ceramic samples increases up to 10 mol% of MgO and then decreases for 15 mol%. It has been further observed that the variation of dielectric constant of glass–ceramic samples with MgO content is exactly opposite to the variation of crystallite size of PbTiO₃ embedded in the glass ceramic-samples.     

Effect of TiO2 on crystallization and mechanical properties of MgO–Al2O3–SiO2 glasses containing P2O5

MgO–Al₂O₃–SiO₂ glass-ceramics have been widely used in military, industrial, and construction applications. The nucleating agent is one of the most important factors in the production of glass-ceramics as it can control the crystallization temperature or the grain size. In this study, we investigated the effect of replacing P₂O₅ with different amounts of TiO₂ on the crystallization, structure, and mechanical properties of an MgO–Al₂O₃–SiO₂ system. The crystallization and microstructure were investigated by differential scanning calorimetry, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were investigated by measuring the Vickers hardness, Young's modulus, and fracture toughness. The results showed that adding TiO₂ favored the precipitation of fine grains and significantly increased the Vickers hardness, Young's modulus, and fracture toughness of the glasses. Introducing an appropriate amount of TiO₂ can make a glass structure more compact, promote crystallization, and improve the mechanical properties of MgO–Al₂O₃–SiO₂ glass-ceramics.     

Formation and crystal growth of needle-like rutile in glass- ceramics

Glass-ceramic, which has negligible dielectric loss, high mechanical strength, excellent drop resistance, low CTE, and low density for lightweight design, is the best option for the back cover of mobile devices in the 5 G era. Herein, the effect of P₂O₅ on the phase separation and crystallization of MgO–Al₂O₃–SiO₂-TiO₂ glass-ceramics is studied. The incorporation of P₂O₅ in the glass structure leads to phase separation, in which the P and Mg-enriched phase was formed in the glass matrix, and promotes the increase of T_g. With the increase of P₂O₅ content, the precipitated crystals change significantly. First, the silicate crystals (Mg₂SiO₄) disappear, whereas the phosphate crystals (LiMgPO₄) emerge when 2 mol% P₂O₅ is introduced. Second, titanate crystal (MgTi₂O₅) can not be observed when 4 mol% P₂O₅ is introduced. The Ti₅O₉ crystals appear simultaneously with LiMgPO₄ crystals and transform to rutile TiO₂ crystals at high temperature. Interestingly, the needle-like rutile TiO₂ crystals, which is 300 nm long and 20 nm wide, have been found in a glass with 4 mol% P₂O₅. The large L/D ratio of needle-like crystals increases the hardness significantly from 6.08 GPa to 7.14 GPa. Similar to other fiber reinforced composites, this needle-like crystals provide a new strategy to improve the mechanical properties of glass ceramics.     

Kinetics and in situ observation of nonisothermal crystallization in Bayan Obo tailing-based nanocrystalline glass-ceramic

In recent years, the preparation of CMAS nanocrystalline glass-ceramics has shown potential as an application of secondary resourcing technology in utilizing Bayan Obo iron ore tailings containing rare earth elements. The crystallization mechanism for nanodiopside-type glass-ceramics was studied via an investigation of the nonisothermal crystallization kinetics of the glass system, combined with the in situ observation of softening and crystallization of the basic glass using a high-temperature laser confocal microscope. The results show that the activation energy of nucleation in the glass system is higher than that of crystal growth by using the Ozawa model. The crystallization mechanism changes as the crystallization fraction increases, that is, from the three-dimensional growth in which the nucleation rate increases with time in an interface-controlled manner (a > 1, b = 1, m = 3) at the initial stage of crystallization to a decreased nucleation rate in a diffusion-controlled growth (a = 0.5, b = 0.5, m = 3) at the middle and later stages. This process involves both surface crystallization and volume crystallization. The crystallization was observed in situ, and it was further confirmed that there exists a critical nucleation temperature between T_g and T_x, which is related to the interface free energy and critical Gibbs free energy difference. When the temperature exceeds the critical value of T_g + 55 K, the system begins to exhibit visible crystallization. With an increase in temperature, the basic glass softened considerably, while the crystal grew significantly. In addition, the surface roughness can be used to characterize the crystallization process, providing a new research method for crystal growth.     

The investigation of the crystalline phases development in Macor® glass-ceramic

The commercially available, machinable, fluormica glass-ceramic, Macor^®, was remelted to produce a glass. This glass was then characterized by differential scanning calorimetry (DSC), combined differential thermal analysis/thermal gravimetric analysis (DTA/TGA), X-ray powder diffraction (XRD) and ¹⁹F magic angle spinning ?nuclear magnetic resonance (MAS-NMR). The Macor^® glass was shown to crystallize to chondrodite (Mg₅F₂(SiO₄)₂), followed by the conversion of chondrodite to norbergite (Mg₃SiO₄F₂) and the conversion of norbegite to a potassium fluorphlogopite phase (KMg₃AlSi₃O₁₀F₂). The glass exhibited an optimum nucleation temperature just above its glass transition temperature, which is indicative of a nucleation route involving amorphous phase separation. The ¹⁹F MAS-NMR spectra showed the fluorine environments being present as F-Mg(3) in the original glass, the chondrodite, norbergite and fluorphlogopite phases, indicating that the fluorine structure is conserved throughout the crystallization process. The activation energies for crystallization were found to be 215, 431 and 251 kJ mol^?1 for chondrodite, norbergite and fluorphlogopite, respectively.