Dilatometric Softening Temperature Research Articles

Cathode-Ray Tube panel glass replaces frit in transparent glazes for ceramic tiles

The disposal of Cathode Ray Tubes (CRT) from end-of-life personal computers and TV screens represents a serious problem in electronic-waste management. As an assembly of different materials, finding a use for each of a monitor's parts is a critical step forward a solution. However, the CRT panel is a silicate glass with a relatively high proportion of alkaline and alkaline-earth oxides, for which recycling is a natural task, and the replacement of frit in ceramic glazes arises as an interesting alternative. In this context, we investigated the effect of CRT panel glass in glazes for ceramic tiles based on a comparative analysis. We replaced up to 40 wt% of commercial transparent frit with CRT panel glass in the formulation of one reference slurry. Chemical analyses were conducted by X-ray fluorescence (XRF) and inductively coupled plasma optical emission (ICP-OES) spectrometry. The thermal expansion coefficient and the glass transition and dilatometric softening temperatures were characterized by dilatometry and compared to such properties calculated as a function of composition, using the SciGlass software and database. 20- and 30-min firing cycles were applied in a fast-firing roller kiln, replicating industrial conditions. The samples transparency was measured by spectrophotometry and compared to the colorimetric parameters of a standard glaze. The maximum content of panel glass possible to add in the transparent glaze formulation without affecting the expected properties was 20 wt%, above which transparency decreased due to heterogeneities. The reformulation of a ceramic glaze with waste CRT panel glass was successful, thus suggesting an interesting approach for disposal of other electronic wastes.

Thermal properties and crystallization of MgO–FeOx–P2O5 glasses

Differential scanning calorimetry (DSC), dilatometry and X-ray diffraction have been used to study thermal behavior and stability of glasses prepared simultaneously in Al2O3 or Pt crucibles in compositional series (40 − x)MgO–xFe2O3–60P2O5 within the concentration range of x = 0–40 mol% Fe2O3. Mossbauer spectra showed that all glasses with Fe2O3 contained both Fe(II) and Fe(III) ions. The contamination glasses from alumina crucibles ranged from 0.3 to 0.9 mol% Al2O3. The replacement of MgO by Fe2O3 resulted in a gradual decrease in glass transition temperature and dilatometric softening temperature, whereas thermal expansion coefficient did not change significantly. The DSC curves showed that all glasses crystallize on heating in the broad temperature range ≈ 560–900 °C. Crystallization temperature decreases with increasing Fe2O3 content. The highest tendency toward crystallization was found for the glass containing 40 mol% Fe2O3. X-ray diffraction measurements showed that the major compounds formed by glass crystallization were Mg(PO3)2, Fe(PO3)3, Fe3(P2O7)2 and FePO4. All thermoanalytical studies showed differences in thermal behavior of glasses prepared in Al2O3 or Pt crucibles.

Characterization of Invert Soda Lime Silica Glasses Containing High Titania Content Together with their Glass Ceramics

Collective structural, optical and thermal properties were investigated for some prepared soda lime silicate glasses containing high TiO2 contents (35, 40, 45%). X-ray diffraction and scanning electron microscopic studies of the prepared heat treated glass-ceramic derivatives were carried out to identify the type of separated crystalline phases and their morphological features. FTIR spectral data indicate the identification of vibrational modes due to the silicate network besides the presence of additional interferences in the wavenumber range 500-800 cm−1 of extra conjugated bands related to Ti-O bending vibrations. X-ray diffraction patterns show the separation of two crystalline silicate phases (wollastonite CaSiO3 and combeite Na2Ca2Si3O9) within the prepared glass-ceramics together with some titanate phases (sodium titanate and calcium titanate). Thermal expansion measurements show the decrease of the dilatometric softening temperature with the increase of TiO2 indicating their housing as TiO6 or TiO5 groups. FTIR spectra are analyzed in relation to the combined identified vibrational modes. Crystallization behavior is related to the dual action of TiO2 acting both as a nucleator for silicate phases and sharing for the formation of some crystalline titanates by direct combination with modifier ions and acting as structural building units.

Influence of Bi<sub>2</sub>O<sub>3</sub> on Crystalline Phase Content and Thermal Properties of Åkermanite and Diopside Based Glass-Ceramic Sealant for SOFCs

Solid oxide fuel cell (SOFC) is an electrochemical energy conversion device which is considered as clean energy source generator with reliability and relatively inexpensive production cost. One of the most important components for planar design SOFC is the hermetic seal that prevents fuel from leaking out of between the stack of fuel cells. Glass-ceramics are attractive materials as sealing materials for this device. The expected coefficient of thermal expansion (CTE) of the glass-ceramic sealants should be between 9 and 12 x 10−6 K−1. Glass – ceramics based on åkermanite (Ca2MgSi2O7) crystalline phase were reported their high CTE value from about 10 to 11.3 x 10−6 K−1. In this study, glass compositions in the CaO-MgO-B2O3-Al2O3-SiO2 system with varying amounts of Bi2O3 from 0 to 10 wt. % were prepared by conventional melting and investigated their properties. The selected compositions were derived from ternary åkermanite–forsterite–anorthite phase diagram. Phase composition and quantitative phase analysis of glass–ceramics were examined by X-ray diffractometer. The onset of crystallization (Tx) and crystallization temperature (Tc) were measured by DTA. The thermal properties of bulk glass samples and heat treated samples at 900 oC for 2 h which were glass transition temperature (Tg), dilatometric softening temperature (Ts), and coefficient of thermal expansion (CTE) were determined by dilatometer. Furthermore, the long-term stability of their CTE was investigated. The samples were continued to soak at 800 °C for 100 h and observed their change in CTE value. The results found that the åkermanite phase tended to increase with increasing amount of Bi2O3 content.

Mixed modifier effect in lithium‐calcium borosilicate glasses

AbstractThe mixed modifier effect (MME) in the lithium‐calcium borosilicate glasses, which have a composition of 0.4[(1−x)Li2O–xCaO]–0.6[(1−y)B2O3–ySiO2] with x in the range of 0~1 and y in the range of 0.33~0.83, is investigated. The MME manifests itself as a positive deviation from linearity in the activation energy of electrical conductivity (Eaσ) and as a negative deviation from linearity in the fraction of four‐coordinated boron (N4), glass transition temperature (Tg), dilatometric softening temperature (Td), Vickers microhardness (Hv), dielectric constant (ε), and dielectric loss (tanδ). Moreover, the deviation, which exhibits a maximum at [CaO]/([CaO]+[Li2O])=0.5, is enhanced with increasing [SiO2]/[B2O3] ratio in the glass network. The observed MME in Tg, Td, and Hv are attributed to the bond weakening in the network; however, the MME in ε, tanδ, and Eaσ are caused by the obstruction of modifier transport in the glass network.

Investigation properties of BaO/RO-Al2O3-R2O3-B2O3-SiO2 glass-ceramic sealants for solid oxide fuel cell

Glass-ceramics are commonly used as sealing materials for planar solid oxide fuel cells (SOFCs). The major requirements of stack and module builders for these materials are the stability of the coefficient of thermal expansion (CTE), the excellent bonding (sticking) behaviour and the absence of volatile ingredients, which can lead to changes of the material properties and the sealing ability. In this study, the thermal stability of glasses in the BaO-Al2O3-La2O3-B2O3-SiO2 system was investigated, to develop a suitable sealing glass for planar solid oxide fuel cell operating at 800–850°C. The developed glasses were characterised through measurement of different properties, coefficient of thermal expansion (CTE), glass transition temperature (Tg), dilatometric softening temperature (Td), crystallisation behaviour during prolonged heat-treatment, density etc. At a target operating temperature of 750°C, the long-term coefficient of thermal expansion (CTE) of one particular composition (G4) was found to be particularly stable, due to devitrification to a mixture of glasses and ceramic phases.

Effects of rare earth oxides on viscosity, thermal expansion, and structure of alkali-free boro-aluminosilicate glass

Effects of rare earth oxides (Y2O3, La2O3, and Er2O3) on the viscosity, thermal expansion, and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer, dilatometry and FT-IR absorption spectra. The results showed that the melting temperature of alkali-free boro-aluminosilicate glasses decreased from 1 697.55 to 1 662.59, 1 674.37 and 1 640.87 °C with the introduction of 1 mol% La2O3, Y2O3 and Er2O3, respectively. However, the glass transition temperature Tg, dilatometric softening temperature Td and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides. At high temperatures, incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm-1 broader, which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts. However, the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.

Structure and properties of barium niobophosphate glasses

Phosphate glasses of the ternary system BaO-Nb2O5-P2O5 were studied in two compositional series, namely 40BaO-xNb2O5-(60-x)P2O5 (series A), with x=0–40mol% Nb2O5, and yBaO-20Nb2O5-(80-y)P2O5 (series B), with y=20–60mol% BaO. Nine homogeneous glassy samples were prepared altogether in both series, and their basic physical properties (density, molar volume, glass transition temperature, dilatometric softening temperature and thermal expansion coefficient) were determined. The chemical durability of the Nb2O5-containing glasses is high and the dissolution rate at 80°C is lower than 4–5×10−8gcm−2min−1. The glass transition temperature of the glasses in series A increased significantly with increasing Nb2O5 content from 324 to 727°C, whereas in the series B with increasing BaO content, Tg increased within the range 620–725°C. The index of refraction increased more steeply in glass series A with increasing Nb2O5 content than in the glass series B. According to the Raman spectra in the glass series A, at low Nb2O5 content niobium forms isolated octahedra NbO6 incorporated in the glass network, but when Nb2O5 content increases, these octahedra are linked into chains and further into three-dimensional clusters. In glass series B, NbO6 octahedra form only NbONbO chains connecting NbO6 octahedra. NbO6 octahedra clustering is reflected also in the 31P MAS NMR spectra of BaO-Nb2O5-P2O5 glasses showing on a non-monotonous transformation of phosphate units in the direction Q3→Q2→Q1→Q0, both with increasing Nb2O5 content in the first A series and BaO content in the second B series.

Microporosity and delamination mechanisms in thermally sprayed borosilicate glass coatings

Conventional enamelling requires both the feedstock powder and the substrate component to be heated one or more times in a furnace at 800–900 °C. The process can degrade the substrate and limit the size of the component to the furnace dimensions, which are serious restrictions on the technology. This study concerns the use of combustion- flame spraying as an alternative technique for enamelling. In this process, the heat source (the flame) is separated from the substrate, which enables much lower substrate temperatures and avoids thermal damage. It also removes the need for furnace treatment and opens up the possibility of on-site enamelling and repair. However, experimental trials showed that thick flame-spray coatings delaminated during cooling and had high microporosities due to quenching stresses at the glass-steel interface and inadequate splat flow of small feedstock particles. The research shows that these adverse mechanisms could be overcome by pre-heating the substrate surface to the dilatometric softening temperature and removing fines from the feedstock powder. The control of these two parameters was found to double the adhesion strength, provide coatings of very similar hardness and fracture toughness to conventional enamel aswell as deposit coatings of over 1mmin thickness for heavy-duty corrosion protection. Thermal spraying is well established for ceramic and metal coatings but the fundamentally different structure of glasses requires a different approach. An advantage of combustion flame spraying shown up by this research is that the high energy of the flame accelerates the particles to a high velocity and the resulting impact forces promote the flow of the glass. As a result, lower substrate temperatures may be used with reduced risk of degradation or higher viscosity glasses may be deposited with enhanced properties. The influence of the type of thermal-spray technique on coating quality is also discussed

Study on the water durability of zinc boro-phosphate glasses doped with MgO, Fe2O3, and TiO2

The water durability of zinc boro-phosphate (PZB) glasses with the composition 60P2O5-20ZnO-20B2O3-xMeO (x = 0, 2, 4, 6 and MeO = MgO, Fe2O3, or TiO2) (mol%) was measured, and PZB glass was studied in terms of its thermal properties, density, and FTIR characteristics. The surface conditions and corrosion byproducts were analyzed using scanning electron microscopy. When MgO, Fe2O3, and TiO2 were doped into the PZB glass, Q2 was decreased and Q1 was increased in the phosphate structure, while the number of BO4 structures increased with increasing MeO content. The density of the PZB glass was increased by the addition of Fe2O3 and TiO2, while the glass transition temperature (T g ) and dilatometric softening temperature (T d ) were increased when additional MgO, Fe2O3, and TiO2 were added. From the weight loss analysis (95 ◦ C, 96 h), TiO2 doped glass showed the lowest weight loss (1.70 × 10 −3 g/cm2) while MgO doped glass showed the highest value (2.44 × 10 −3 g/cm2), compared with PZB glass (3.07 × 10 −3 g/cm2). These results were discussed in terms of the Me n+ ions in the glass structure, and their different coordination numbers and bonding strengths.

Thermal expansion behavior of Ge‐Sb‐Se glasses in a compositional range for molded infrared lens applications

AbstractThe thermal expansion coefficient (TEC) of Ge‐Sb‐Se glass, within a compositional range suitable for molded lenses capable of transmitting long‐wavelength infrared, was analyzed to assess compositional dependence. Unlike other thermal properties, eg, glass transition temperature and dilatometric softening temperature, which are correlated mostly with germanium content, the TEC turned out to behave most sensitively with selenium content. The thermal expansion behavior of this glass was evaluated based on two structural parameters: the mean coordination number and average bond energy (ABE). It was verified that the relation between TEC and these structural parameters needs to be distinguished in terms of homopolar Se‐Se bonds. Specifically, the TEC tends to decrease monotonically as the mean coordination number increases, and there are relatively small discrepancies between Se‐sufficient and Se‐deficient compositions. The TEC of the Se‐sufficient glass appears to have a relatively well‐defined correlation with the ABE: the TEC decreases as the ABE increases. However, a much weaker correlation between the TEC and ABE is observed in the Se‐deficient glass. The observed thermal expansion behavior of this glass is delineated, with a particular focus on its connection to the structural role of the Se atoms.

Influence of (CoO, CaO, B2O3) additives on thermal and dielectric properties of BaO–Al2O3–SiO2 glass–ceramic sealant for OTM applications

The efficiency of glass ceramic sealants plays a crucial role in high temperature applications' performance and durability, such as oxygen separation from air. In order to develop suitable sealants, operating at about 950°C, several glass–ceramics with different compositional additives and ratios in BaO–Al2O3–SiO2 system have been prepared and investigated. The effect of additive oxides (CaO, CoO, B2O3) as network modifiers on the thermal and dielectric properties of BaO–Al2O3–SiO2 glass–ceramic for further oxygen transport membrane (OTM) applications was evaluated and discussed. The introduction of additives has evident effects on the main crystalline phases and physical properties of the glass–ceramics. Among these systems, B2O3-rich BAS system (BABS) can be densified at the sintering temperature below 700°C through viscous sintering. Also, BABS shows the lowest dilatometric softening temperature at 675°C, which can be explained by a fast densification associated with shrinkage of 25%. After devitrification for 200h at 950°C, BABS exhibits excellent thermal stability, suffering a weight loss of maximum 0.04%. It has the highest conductivity and resistivity, a high dielectric constant of 67.8 and a loss of 0.029 at 10MHz, which provide an attractive insulating feature for many technological applications. However, considering all other properties investigated besides the electric ones, only B2O3-rich BAS meets the requirements for use as a sealant for BSCF membrane. Low softening temperature of BABS opens more ways for adding additives to tailor its functional properties, which enables it to being used as sealant material for OTM applications.

Effect of Bi<sub>2</sub>O<sub>3</sub> on Thermal Properties of Barium-Free Glass-Ceramic Sealants in the CaO-MgO-B<sub>2</sub>O<sub>3</sub>-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> System

Barium-free glass-ceramic sealants for the planar solid oxide fuel cell (pSOFC) have attracted considerable attention to avoid the crystallization of the high coefficient of thermal expansion (CTE) BaCrO4; reaction product at the interface between barium-containing glass-ceramic sealants and Crofer22 APU interconnect, which decreases the long-term mechanical stability of the sealant. In this study, Barium-free glass-ceramic sealants in the CaO-MgO-B2O3-Al2O3-SiO2 system with varying amounts of Bi2O3 from 0 to 10 wt. % were prepared by conventional melting and their thermal properties were investigated. The glass transition temperature (Tg), dilatometric softening temperature, and coefficient of thermal expansion (CTE) were determined by a dilatometer. The Tg, onset of crystallization (Tx) and crystallization temperature (Tc) were obtained from DTA. Results of phase analysis by X–ray diffraction of glasses after thermal treatment at 900 oC for 2 h indicated that the major phase of all glasses was diopside (MgCaSi2O6) and minor phases were åkermanite (Ca2MgSi2O7) and forsterite (Mg2SiO4). The Tg of the fabricated glasses tended to decrease with increasing Bi2O3 content while the CTE of glasses increased after the thermal treatment and was in the range of requirement for SOFC sealant.

The structure and properties of SnF2–SnO–P2O5 glasses

SnF2–SnO–P2O5 glasses with low glass transition temperature (Tg) were prepared in this paper. The effect of composition and melting time on the properties of these glasses was studied. X-ray diffraction (XRD) indicated that these prepared samples were glasses regardless of the composition and melting time. The properties of these glasses such as Tg, dilatometric softening temperature (Tf), thermal expansion coefficient (α) and density (ρ) were tested. The structure of these glasses was studied by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA). The glasses' structure and network dimension were supposed to play a critical role on the properties of the glasses. The fluorine and hydroxyl can decrease the network dimension of the glasses and thus decrease the Tg values. While, the oxidation of Sn2+ to form the Sn4+ could increase the network dimension of glasses and thus increase the Tg values.

Preparation and characterization of novel foamed porous glass-ceramics

Foamed glass-ceramics without using foaming agent have been synthesized in a novel glass system of SrO-CaO-Al2O3-TiO2-B2O3-SiO2-P2O5-MxOy (where M=Ba, Mg, La, Ce and Ni) by a simple process of powder sintering. The glass and glass-ceramics are characterized by dilatometry, differential scanning calorimetry (DSC), heating stage microscopy (HSM), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), optical microscopy and Fourier transformed infrared spectroscopy (FTIR). All the glasses formed are amorphous and the glass transition temperature and dilatometric softening temperature of these glasses are found to be in the range 673–678°C and 706–728°C respectively. The glasses are highly stable as indicated by the DSC evaluated glass stability parameters of the range 195–240°C. Quantitative sintering study of glass powder compacts revealed swelling in the samples with NiO and CeO2 corresponding to a geometry change of 75 and 108% around 900°C respectively. With reference to this finding the glass powder compacts are heated to 900°C and the foamed glass-ceramics are obtained. Characteristic crystalline silicate phases have been identified in the XRD studies and their microstructures are recorded by FESEM. Optical microscope study of the foamed samples revealed formation of bigger foamed cavity with residual pores in samples with NiO and CeO2 in comparison to samples with BaO, MgO and La2O3. The mean pore diameters of the samples with NiO and CeO2 are determined to be 43 and 32μm, and their respective porosities are 2.34 and 1.82cm3/g respectively. Thus NiO and CeO2 are found to be very effective to obtain foamed glass-ceramics without using foaming agent by the viscous flow sintering of fine glass powder compacts along with the reduction of the respective polyvalent ions.

Effects of In-situ Generated Coinage Nanometals on Crystallization and Microstructure of Fluorophlogopite Mica Containing Glass‒Ceramics

The effects of in-situ generated coinage nanometals (Cu, Ag and Au) on crystallization behavior, microstructure, thermal and mechanical properties of SiO2–MgO–Al2O3–B2O3–K2O–MgF2 (BMAPS) glass‒ceramics were systematically studied. On addition of coinage nanometal, the glass transition temperature (Tg) is increased by 20–30 °C, crystallization temperature (Tc) by 30–50 °C and dilatometric softening temperature (Td) by 10–25 °C. It was found that the density of Cu-containing glass was 2.59 g cm−3 and for other glasses it was in the range of 2.56–2.57 g cm−3. From the non-isothermal differential scanning calorimetry study, the activation energy of crystallization for BMAPS base glass was calculated as 344 kJ/mol, and changed to 406, 334 and 274 kJ/mol on addition of Cu, Ag and Au-nanometals, respectively. Crystals evolved in the opaque BMAPS glass‒ceramics derived by controlled heat treatment, were identified as fluorophlogopite mica (KMg3(AlSi3O10)F2) by X-ray diffraction (XRD) technique and confirmed by Fourier transformed infrared spectroscopy. Presences of copper, silver and gold nanometals were also identified by XRD technique. It is found from field emission scanning electron microscopy that the interlocked grain like microstructure developed in BMAPS glass‒ceramics (being heat-treated at 1050 °C for 4 h) changed to denser house-of-cards like microstructure (containing smaller sized mica crystals) on addition of coinage nanometals. Density of BMAPS base glass‒ceramic was 2.60 g cm−3 and marginally changed to 2.61–2.62 g cm−3 on addition of Cu, Ag and Au-nanometals. The change in microstructure resulted in the decrease of Vickers micro hardness value from 5.37 to 4.12, 4.20 and 4.58 GPa on addition of Cu, Ag and Au, respectively. Coinage nanometal doped mica glass‒ceramics containing interlocked microstructure with higher thermal expansion coefficient, hence, is suitable for high temperature sealing application (like solid oxide fuel cell).

Synthesis and properties of ZnTe and Eu3+ ion co-doped glass nanocomposites

In this study, ZnTe (II-VI) semiconductor and Eu+3-ion co-doped borosilicate glass has been prepared in the SiO2-K2O-CaO-BaO-B2O3 glass system followed by controlled heat-treatment to produce glass nanocomposites. Glass transition temperature and crystallization peak temperature have been evaluated using DSC analysis. Dilatometric studies were carried out to evaluate thermal expansion co-efficient, glass transition temperature, and dilatometric softening temperature and found to be 10.7 × 10−6/K, 580° C and 628° C, respectively. TEM micrographs demonstrate formation of nano sized crystallites of less than 50 nm. The ZnTe crystal formation also established through selected area electron diffraction (SAED) analysis and high resolution images obtained through TEM studies. With increasing heat treatment time, optical transmission cut-off wavelength (λcut-off) shifted towards higher wavelength. Excitation spectra were recorded by monitoring emission at 613 nm corresponding to the 5D0 → 7F2 transition. An intense 394 nm excitation band corresponding to the 7F0 → 5L6 transition was observed. Emission spectra were then recorded by exciting the glass samples at 394 nm. When the glass is heat-treated for 30 min at 610° C, a 6-fold increase in the intensity of the red emission at 612 nm has been observed, which is attributed to the segregation of Eu3+ ions into the low phonon energy ZnTe crystallites and as the size of the nanocrystals is smaller than the size of the exciton, quantum confinement effect is visible. Further increase in heat-treatment duration led to decrease in luminescence intensity due to the growth of larger size crystals. 5D1 → 7F0 transition is visible only in the samples heat-treated for 30 min and 1 h, which is a characteristic of presence of Eu3+ ions in the low phonon energy ZnTe crystal sites. The micro hardness of the precursor glass and glass nanocomposites was evaluated; base glass shows hardness of 6.7 GPa and hardness of heat-treated glass nanocomposites has been found to decrease with increase in heat-treatment duration (5.5-5.3 GPa). However, mechanical properties are found to be suitable for device applications.

Thermal, optical and structural properties of Tb doped zinc aluminum phosphate glasses

Zinc aluminum phosphate (ZAP) glasses and Tb3+ ions doped zinc aluminum phosphate (Tb doped ZAP) glasses have been prepared by melt quenching method. The effects of the ZnO and Tb2O3 content on the thermal, optical and structural properties of the ZAP, (90−x) P2O5–10Al2O3–xZnO (x=30, 35, 40mol%), and the Tb doped ZAP, (90−x)ZAP xTb2O3, vitreous systems were investigated. It was found that the glass transition temperature (Tg) and glass dilatometric softening temperature (Td) were lowered as ZnO content increased. The addition of Tb3+ ions also increases the Tg and Td, and the coefficient of thermal expansion (CTE) is reduced to less than 5×10−6/°C under higher Tb2O3 content. Higher refractive index (n~1.55) is achieved for Tb doped ZAP under higher ZnO and Tb2O3 content. Besides, the Tb doped ZAP shows greater chemical durability with the dissolution rate as low as 3×10−7g/cm2-min. Analyses from FTIR, Raman and NMR spectroscopies are discussed in comparison with the quantitative results of bridging oxygen (BO) and non-bridging oxygen (NBO) by O1s-XPS. It was found that the metaphosphate (Q2) dominates the ZAP glasses; however, the pyrophosphate (Q1) becomes significant for the Tb doped ZAP under addition of higher Tb2O3 content, leading the enhanced glass network. Highest Tb3+/Tb4+ ratio with value of 2.33 is observed for (90−x)(50P2O5–10Al2O3–40ZnO)–xTb2O3 (x=3), which exhibits much enhanced emission band at 545nm. Also, the sensitized effect of ZnO on the emission band is verified. The enhanced emission properties suggest that the Tb doped ZAP glass is a promising material for the application in green LED device by modulation of Tb composition.

Preparation method and thermal properties of samarium and europium-doped alumino-phosphate glasses

Abstract The present work investigates alumino-phosphate glasses from Li2O–BaO–Al2O3–La2O3–P2O5 system containing Sm3+ and Eu3+ ions, prepared by two different ways: a wet raw materials mixing route followed by evaporation and melt-quenching, and by remelting of shards. The linear thermal expansion coefficient measured by dilatometry is identical for both rare-earth-doped phosphate glasses. Comparatively to undoped phosphate glass the linear thermal expansion coefficient increases with 2 × 10−7 K−1 when dopants are added. The characteristic temperatures very slowly decrease but can be considered constant with atomic weight, atomic number and f electrons number of the doping ions in the case of Tg (vitreous transition temperature) and Tsr (high annealing temperature) but slowly increase in the case of Tir (low annealing temperature–strain point) and very slowly increase, being practically constant in the case of TD (dilatometric softening temperature). Comparatively to undoped phosphate glass the characteristic temperatures of Sm and Eu-doped glasses present lower values. The higher values of electrical conductance for both doped glasses, comparatively to usual soda-lime-silicate glass, indicate a slightly reduced stability against water. The viscosity measurements, showed a quasi-linear variation with temperature the mean square deviation (R2) being ranged between 0.872% and 0.996%. The viscosity of doped glasses comparatively to the undoped one is lower at the same temperature. Thermogravimetric analysis did not show notable mass change for any of doped samples. DSC curves for both rare-earth-doped phosphate glasses, as bulk and powdered samples, showed Tg values in the range 435–450 °C. Bulk samples exhibited a very weak exothermic peak at about 685 °C, while powdered samples showed two weak exothermic peaks at about 555 °C and 685 °C due to devitrification of the glasses. Using designed melting and annealing programs, the doped glasses were improved regarding bubbles and cords content and strain elimination.

Physical properties of Sb2 O3 - P2 O5 glasses

Some physical properties of a Sb2 O3 -P2 O5 glass were analyzed. A glass with composition (mol%) 75Sb2 O3 25P2 O5 were melted in an electrical furnace and in glassy carbon crucible at 1000 . Samples were cutted, lapped and polished with cerium oxide and using ethylene glycol as polishing fluid, since the glass presents some hygroscopicity. Using the Archimedes principle and ethylene glycol again as immersion fluid, the density of the glass was determined to be ρ= (4,774±0,001) g/cm^3. The pulse-echo method was applied to determine the longitudinal and transversal ultrasonic velocities. These values enable the calculation of the Young modulus, E, and the Poisson coefficient, ν: E = (39±2) GPa and ν = 0,22±0,01. The experimental value of the hardness was obtained from measurements of the Vickers impression diagonals, d, produced by applying loads, P , up to 500 g: H = (2,31±0,04) GPa. Dilatometric measurements indicate that the glass transition temperature, Tg, is about 300 , and the dilatometric softening temperature, Td, is 330 . The coefficient of thermal expansion, α, between 150 and 270 is 17.3 x 10−6 °−1 . Once the glass is transparent, the refractive index was obtained by using an optical microscope. This values is roughly given: n = (1,96±0,08). Therefore one can conclude that, although the low values of the Young modulus and hardness, the high value of the refractive index demonstrates that this glass can present interesting optical applications.