Dilatometric Softening Temperature Research Articles

Preparation and characterization of strontium-doped bismuth borate glasses

Employing the melt quenching method, new bismuth borate glass compositions denoted as (40+x)Bi2O3–(60-x-y)B2O3–ySrO, with x and y ranging between 0 to 20 mol%, were synthesized. The X-ray Diffraction analyses confirmed the amorphous nature of all glass samples, indicating the absence of long-range order typically seen in crystalline materials. Concurrently, the Fourier-transform Infrared Spectroscopy examinations unveiled the existence of fundamental structural units within the glasses, including BO3 and BO4 trigonal and tetrahedral units, as well as BiO3 and BiO6 polyhedra, suggesting a complex network structure. Differential Thermal Analysis (DTA) and dilatometry assessed the glasses' thermal properties. DTA demonstrated the glasses' high thermal stability, with a stability value of up to 106°C, noting that stability improves with more SrO. Dilatometry analyses revealed these glasses exhibit a high thermal expansion coefficient, ranging from 8.69 to 10.7 ppm/°C, alongside relatively low glass transition temperatures between 362 and 432°C and dilatometric softening temperatures spanning from 380 to 447°C. Density measurements were conducted, followed by molar volume and oxygen packing density calculations, to glean further insights into the samples. Compared to other heavy-metal oxide glasses, the glasses examined in this study exhibited notably high-density values, ranging between 6.279 and 7.476 g/cm3 .

Effects of composition on the structure, thermal and some physical characteristics of Bi2O3-B2O3-ZnO-SiO2 glasses

The influence of composition on the structure, thermal, and some physical characteristics of bismuth borate glasses, formulated as 55Bi2O3–(35-x-y)B2O3–(5+x)ZnO–(5+y)SiO2 (where 0 ≤ x, y ≤ 15 mol%), was investigated. Comprehensive analyses were conducted using techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis (DTA), and Dilatometry. XRD confirmed the amorphous nature of the glass samples, while FTIR spectroscopy revealed that the glasses are primarily composed of BO4, BO3, BiO6, BiO3, ZnO4, and SiO4 structural units. DTA provided further evidence of the samples' glassy state and insights into key temperatures like glass transition (Tg), crystallization (Tc), and melting (Tm). The study finds that substituting B2O3 with SiO2 increases all characteristic temperatures, whereas replacing it with ZnO decreases Tg and Tc but increases Tm. The maximum thermal stability, indicated by a ΔT of 99°C, was observed in the glass with a 55Bi2O3–20B2O3–20ZnO–5SiO2 composition. Dilatometric measurements showed that the investigated glasses have a high coefficient of thermal expansion (10.0–10.7 ppm/°C) values, a low glass transition temperature (345–376°C), and a low dilatometric softening temperature (364–392°C). Additionally, the density and molar volume of the samples were accurately determined.

Influence of barium substitution on the physical, thermal, optical and luminescence properties of Sm3+-doped metaphosphate glasses for reddish orange light applications.

Our present study focuses on examining the thermal, structural and luminescent characteristics of sodium barium metaphosphate glasses doped with Sm3+. Glass samples with molar compositions (100 - y)[(50P2O5)-(50-xNa2O)-(xBaO)]-ySm2O3, where x = 20, 25, 30, 35, 40 and y = 0.3 and 1% were first synthesized by conventional melt quenching and later dehydroxylated under a constant N2 flow to ensure final glasses with a very high degree of chemical and optical homogeneity and free of water. Upon the addition of BaO and Sm2O3, refractive index, molar mass, density, glass transition temperature and dilatometric softening temperature exhibited an increase, whereas the coefficient of thermal expansion showed a decrease. The FTIR spectra analysis reveals a network depolymerization that intensifies with rising BaO concentration, ultimately transitioning from a modifier oxide to a glass-forming element, at higher BaO concentrations. All doped samples exhibited prominent absorption bands in the visible (VIS) and near-infrared (NIR) regions, as revealed by the optical absorption spectra. The Na2O modifier demonstrated greater influence on Sm3+ emission compared to BaO, a phenomenon that can explained by the moderation of the local ligand field strength resulting from this substitution. With an increase in Sm2O3 concentration from 0.3 to 1 mol%, the experimental lifetimes of the 4G5/2 level decrease, primarily attributed to the presence of energy transfer mechanisms. A discussion of Judd-Ofelt parameter analysis and glass radiation properties will be presented.

Exploring the impact of Bi2O3 addition on the thermal properties and crystallization behavior of lead borosilicate glasses

Novel heavy-metal oxide glasses with different compositions, specifically (80-x)PbO– xBi2O3–10B2O3–10SiO2, where x ranges from 0 to 60 mol%, were synthesized using a conventional melt-quenching technique. The amorphous nature of these glasses was confirmed through X-ray diffraction analysis. Additionally, infrared spectra were obtained for the prepared samples to explore their structural characteristics. Differential thermal analysis was performed to investigate the characteristic temperatures of the glasses, including the glass transition temperature, melting temperature, onset crystallization temperature, and peak crystallization temperature. The addition of Bi2O3 shifts the characteristic temperatures to higher values and affects the crystallization process and phases formed. Parameters like ΔT, KH, and KSP are used to evaluate and quantify glass stability. Dilatometric measurements demonstrated that substituting PbO with Bi2O3 in the glass composition resulted in an increase in glass transition temperature and dilatometric softening temperature, as well as a decrease in the coefficient of thermal expansion. Furthermore, we determined the density and calculated the molar volume of the samples. These findings deepen our understanding of the thermal behavior, glass stability, and structure-property relationships in lead borosilicate glasses with Bi2O3, facilitating the development and customization of glass compositions with desired thermal and physical characteristics for specific applications.

Structure, thermal and crystallization behavior of lead-bismuth silicate glasses

Lead-bismuth silicate glasses were synthesized using a standard melt-quenching technique, varying the compositions within the range of (80-x-y)PbO–(10+x)Bi2O3–(10+y)SiO2, where x and y were between 0 and 20 wt%. The glasses were subjected to comprehensive analysis, including X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, and dilatometry, to investigate their crystallization behavior, thermal properties, and structure. The obtained glass samples were confirmed to be amorphous through X-ray diffraction and scanning electron microscopy. Fourier-transform infrared spectra analysis indicated that the glasses consisted mainly of PbO4, BiO6, and SiO4 structural units. Differential thermal analysis curves were used to estimate the glass transition, crystallization, and melting temperatures, and the results showed increased thermal stability and decreased crystallization tendency with increasing SiO2 content in the glass. X-ray diffraction analysis was utilized to identify the specific crystalline phases that were formed after the glass was subjected to heat treatment. Dilatometric measurements demonstrated that the investigated glasses possess a wide range of coefficient of thermal expansion values (6.8–11.1 ppm/°C), a low glass transition temperature (335–475°С), and a low dilatometric softening temperature (355–505°С). These results have significant implications for developing oxide glasses with specific thermal characteristics suitable for a wide range of applications.

Synthesis, structure and properties of PbO–PbF2–B2O3–SiO2 glasses

The structure, thermal and some physical properties of lead fluoroborate glasses containing 30 mol% SiO2 have been investigated by differential thermal analysis, X-ray diffraction and Fourier-transform infrared spectroscopy. The glasses were prepared by the conventional melt-quenching method. Fourier-transform infrared spectroscopy results showed that the network of these glasses consists mainly of BO3, BO4, SiO4, and PbO4 structural units. The thermal stability of the glass samples determined by differential thermal analysis was found to be about 80°C. Dilatometric measurements showed that the glass transition temperature and dilatometric softening temperature decrease with increasing lead content, whereas the coefficient of thermal expansion increases. The density and molar volume increased with the increase in lead content. The conductivity of the investigated glasses mainly depends on the mobility of F– and Pb2+ ions. The variation in volume resistance upon changing the composition has been correlated with the structural changes in the glass network. The results obtained in this study indicate that the investigated glasses can be potential candidates for advanced technologies as solder and sealing materials.

Influence of R2O3 (R=Al, La, Y) on the structure and properties of strontium borosilicate glasses

The influence of R2O3 (R=Al, La, Y) on the structure, thermal, and some physical properties of strontium borosilicate glasses have been investigated by differential thermal analysis, X-ray diffraction, and Fourier-transform infrared spectroscopy. Fourier-transform infrared spectroscopy results showed that the network of the investigated glasses consists mainly of BO3, BO4, and SiO4 structural units. The influence of R2O3 on the properties of strontium borosilicate glasses depends on the structural role of R3+ ions. The experimental results suggest that Al3+ ions act as intermediate in the investigated composition range, while La3+ and Y3+ ions act as modifiers and depolymerize the glass network. The obtained results showed that the glass transition temperature (610–6600С), dilatometric softening temperature (640–6750С), and molar volume (25.03–29.22 cm3/mol) values of the investigated glasses were increased with equimolar substitution of SrO by R2O3. The thermal expansion coefficient (6.8–9.5 ppm/K) of the investigated glasses was found to decrease with increasing the R2O3 content. The obtained results showed that the density (3.03–3.68 g/cm3) values of the investigated glasses were increased with increasing the Y2O3 and La2O3 content and decreased with increasing the Al2O3 content. The tendency to crystallize is higher in glasses containing La2O3 compared to glasses containing Y2O3 or Al2O3. The results obtained in this study indicate that the investigated glasses can be potential candidates for advanced aerospace and electronic applications as heat-resistant electrical insulating glass- and glass-ceramic-to-metal seals and coatings.

Thermal, structural and crystallization study of Na2O–P2O5–Nb2O5 glasses

The present investigation deals with the study of the structure, properties and thermal behaviour of Na2O–P2O5–Nb2O5 glasses prepared in the compositional series 40Na2O-(60-x)P2O5-xNb2O5 (x=0–40 ​mol% Nb2O5). The modification of starting 40Na2O–60P2O5 glass by Nb2O5 revealed changes both in the structure and properties. The glass density steeply increases with increasing Nb2O5 content while the molar volume decreases. Parent sodium ultraphosphate glass was covered with a thin layer of partially hydrolysed glass in air. The chemical durability of Nb2O5 containing glasses was high. The replacement of P2O5 by Nb2O5 resulted in a gradual increase in the refraction index as well as in an increase in glass transition temperature and dilatometric softening temperature. DSC measurements demonstrated that glasses crystallize under heating in the temperature range of 330–880°C. The lowest thermal stability was found for the glass containing 40 ​mol% Nb2O5. The Raman and NMR spectra indicated that the structure of 40Na2O–60P2O5 glass is formed mainly by Q2 and Q1 phosphate units interconnected by P–O–P bonds. The replacement of P2O5 by Nb2O5 leads to depolymerization and the partial transformation of Q2 units into Q1 units and finally to isolated Q0 units. Nb2O5 forms in the glass structure NbO6 octahedra.

Structural and crystallization behavior studies on unfamiliar LiF–B2O3 glasses

Glasses from the binary high LiF–B2O3 system with variable LiF contents (10–55 mol%) were prepared by normal melting-annealing technique. Optical, FTIR spectral properties were measured for the glasses in addition to thermal expansion parameters were derived to be able to convert glassy samples to their corresponding glass-ceramic derivatives. FTIR, X-ray diffraction and SEM were carried out for the prepared heat-treated glass-ceramics to derive their structural building groups and types of crystalline phases formed by controlled heat treatment regime. Optical spectra of the prepared glasses show only distinct UV absorption peaks which are related to unavoidable contaminated traces of impurities of Fe3+ ions. FTIR spectra reveal distinct extended vibrational bands within the mid-region 400-1600 cm−1 comprising both of triangular and tetrahedral borate groups (BO3, BO3F) beside the possibility of sharing of (LiF4) groups at high LiF content. Thermal expansion measurements indicate the changes of the dilatometric softening temperatures with the LiF content but with some derived variations depending on the constituents housing in the network structure. X-ray diffraction patterns data reveal the appearance of lithium borate crystalline phase at low LiF content and at high content both two crystalline phases of lithium borate Li2B4O7 (Diomignite) and LiB3O5 beside crystalline lithium fluoride (LiF) are identified. This result refers to the distinct action of both lithium ions (Li+) and fluoride ions (F−) as initiator to produce phase separation, ease of nucleation and followed by crystallization, similar to the behavior of Li2O within borate and silicate glasses. SEM images support the X-ray diffraction data revealing different crystalline phases with variable texture at high LiF content.

Preparation and characterization of glasses from the binary sodium fluoroborate system NaF–B2O3 within the range (10–50 mol% NaF) assessed by structural FTIR, optical and thermal properties and effects of gamma irradiation

Extended glasses from the binary system (NaF-B2O3) with (10→50 mol% NaF) were synthesized by the traditional melting-annealing route. These unfamiliar glasses with high extended NaF contents than Na2O were characterized by multi-techniques including optical and FTIR spectral analysis beside measurements of their thermal expansion parameters. The optical (UV–visible) spectra of the glasses reveal obvious transparency except for the appearance of distinct UV absorption due to unavoidable trace ferric ions impurities present within the laboratory chemicals. Structural FTIR spectra indicate that NaF primarily acts the same as Na2O progressively converting some of the BO3 units to produce tetrahedral (BO3F) units and then at a high percent of NaF is assumed to form additional (NaF4) groups and hence the intensity of the bands within the range 800–1200 cm−1 due to combined tetrahedral groups (BO4 + NaF4) is always higher than that for the peaks at the range 1200–1600 cm−1due to vibrational BO3 groups. The thermal expansion data reveal that the dilatometric softening temperature primarily increases due to the formation of compact tetrahedral (BO3F) groups. It is obvious that this unfamiliar (NaF–B2O3) glass does not show an anomalous behavior as that reported for (Na2O–B2O3) glassy system and other alkali-B2O3 glasses in their thermal expansion properties. Gamma irradiation did not show any distinct variations in the FTIR spectra indicating the stability of the structural building groups in this NaF–B2O3 glass system. On the other hand, the optical spectra show the displacement of one of the two broad bands in the UV spectra which is assumed to be due to a photochemical reaction between some Fe3+ ions present as trace impurities and formed freed electrons during the irradiation process.

Phase separation and the properties of lithium strontium silicate glasses

The immiscibility region covers most of the region of glass formation in the lithium strontium silicate system. Although the density, refractive index, and thermal expansion coefficient are insensitive to the presence of phase separation, the glass transformation temperature can be used to determine the limit of immiscibility in this system. The dilatometric softening temperature was used to determine the boundary the limit of connectivity of the silica-rich phase. The electrical conductivity and activation energy for conduction were used to determine the limit of connectivity of the lithium-rich phase.

Effect of BaO substitution for CaO on the structural and thermal properties of SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications

The present study replaced 3.30 and 9.00 mol.% BaO for CaO in a SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications. Variations of the glass structure, thermal properties, cytotoxicity, and radiopacity of glasses were studied. As demonstrated by the results, upon adding barium oxide to the glass structure, the weight density increased significantly, while a slight decrease in oxygen density was determined. Introducing barium oxide into glass composition did not cause any considerable change in the spectra of FTIR and Raman. It was demonstrated that the amount of bridging oxygen in the glass structure remained quite unaffected. The hot stage microscopy evaluations revealed further shrinkage of barium-containing frits due to lower viscosity and hence, higher viscous flow of these glasses. By substituting barium oxide for calcium oxide and increasing its concentration, the glass transition temperature (Tg) and the dilatometric softening temperature (Td) decreased, while the thermal expansion coefficient increased. Moreover, upon substituting 9 mol.% barium oxide for calcium oxide, a 30 °C reduction in maximum sintering temperature (Tms) of the glass was obtained, whereas the shrinkage rate was increased 1.7 times. It was indicated that the sintering process of barium-incorporated glasses would easily proceed without any phase crystallization. The barium-incorporated glasses exhibited more radiopacity. Additionally, no cytotoxic effect was caused by the substitution, and the Ba-containing glasses could be used for biomedical applications and implant coating as well.

Development and characterisation of a Y2Ti2O7-based glass-ceramic as a potential oxidation protective coating for titanium suboxide (TiOx)

A silica-based glass-ceramic, with Y2Ti2O7 as the major crystalline phase, is designed, characterised and tested as an oxidation-protective coating for a titanium suboxide (TiOx) thermoelectric material at temperatures of up to 600 °C. The optimised sinter-crystallisation treatment temperatures are found to be 1300 °C and 855 °C for a duration of 30 min, and this treatment leads to a glass-ceramic with cubic Y2Ti2O7 and CaAl2Si2O8 as crystalline phases. An increase of ~270 °C in the dilatometric softening temperature is observed after devitrification of the parent glass, thus further extending its working temperature range.Excellent adhesion of the glass-ceramic coating to the thermoelectric material is maintained after exposure to a temperature of 600 °C for 120 h under oxidising conditions, thus confirming the effectiveness of the T1 glass-ceramic in protecting the TiOx material.

Infrared transmission and refractive index dispersion of mixed-chalcogen Ge-Sb-S-Se glasses for use in molded lens applications

In an effort to augment thermal and mechanical properties of ternary Ge-Sb-Se glass for use in molded lens applications, mixed-chalcogen Ge27.5Sb12.5SxSe60-x glasses have been investigated in this study with a particular attention paid to refractive index dispersion as well as infrared transmission edge. Changes in Vickers hardness, glass transition temperature, dilatometric softening temperature and thermal expansion coefficient are elucidated in terms of structural evolutions that sulfur induces. Infrared transmission edge blueshifts upon the addition of sulfur, which can be nicely interpreted in connection with average bond energy and molar mass of a given composition based on a postulation that this glass behaves as a single average harmonic oscillator in shaping multiphonon absorption. Refractive index at the long-wavelength infrared range becomes more dispersive with increasing sulfur content in these sulfur-selenide glasses, and thereby their dispersion can be pinpointed via adjusting S content. The Abbe diagram in the long-wavelength infrared region is extended towards the high-dispersion side, thus enhancing practicality of the chalcogenide glasses as in the form of lens and/or filter for the thermal imaging applications.

Preparation and characterization of invert ZnO–B2O3 glasses and its shielding behavior towards gamma irradiation

Binary zinc borate glasses with invert compositions (50–75 mol % ZnO) were prepared by melting and annealing technique. The glasses were collectively characterized by measuring and identifying their structural building groups through FTIR spectroscopy and their optical transparency beside also their thermal expansion parameters. FTIR spectra reveal compact vibrational bands within the mid region 400-1700 cm−1 reflecting both triangular and tetrahedral borate groups beside the sharing of ZnO as either modifier oxide or as B–O–Zn linkages and possibly ZnO4 groups. The optical absorption measurements reveal that the studied undoped ZnO–B2O3 glasses show distinct UV absorption extending from 200 to 370 nm with three peaks and these UV absorption peaks are related to unavoidable trace iron (Fe3+) impurities contaminated within the chemicals used for the preparation of the zinc borate glasses. The optical absorption spectra after gamma irradiation with a dose of 5 Mrad reveal the maintenance of the UV spectra identified before irradiation with the appearance of a minor curvature at 510 nm in the spectra of two samples and disappeared at high ZnO contents. Such optical spectral result after irradiated refers to suggested shielding effect towards gamma irradiation with high ZnO content in the studied invert compositions. Both the dilatometric softening temperatures and density data show obvious increase with the first increase of ZnO content up to 70% and then reveal constancy. This behavior is correlated with the mode of housing Zn2+ ions in the network structure which is assumed to form some ZnO4 groups at high percent of ZnO giving compactness to the network of such glasses.

Structural FTIR spectra and thermal properties of CdO–B2O3 glasses doped with LiF, CaF2 or TiO2, together with X-ray diffraction and SEM investigations of their glass–ceramic derivatives

Binary cadmium borate (CdO 40–B2O3 60 mol%) glass together with samples with the same basic composition and doped with 2% of either LiF, CaF2 or TiO2 were prepared by melting-annealing technique. Samples of these prepared glasses were thermally heat-treated to convert them to their corresponding glass–ceramic derivatives. FTIR spectral measurements were carried out to identify the constitutional network building units. IR results indicate the identification of both triangular BO3 and tetrahedral BO4 groups in their characteristics vibrational different wavenumbers. These IR vibrational spectra were assigned to their origin and they confirm that CdO like any alkali or alkaline earth oxide shares in the modification of some BO3–BO4 groups to their specific limit. The dopants show minor variations on the IR spectra due to their low percent. X-ray diffraction patterns identify the crystalline phases which were separated during thermal heat-treatment and the dopants were efficient in acting as nucleating agents and sharing in the crystalline phases formed. The base glass–ceramic is composed of cadmium metaborate only while the dopants change this phase to cadmium pyroborate beside a lithium borate or calcium borate phases while with TiO2 forms brookite crystalline phase beside cadmium pyroborate. Thermal expansion measurements for the studied glasses reveal similar progressive increase in thermal expansion coefficient, but the dilatometric softening temperatures exhibit distinct decrease with the dopants supporting the assumption that the dopants are situated in modifying positions. SEM technique was performed to ensure the morphological structures which exist along with addition of different dopants.

Physical properties and structural studies of lithium borophosphate glasses containing TeO2

This work presents a study on the structure, thermal behavior and properties of (100-x)[0.5Li2O-0.1B2O3-0.4P2O5]-xTeO2 glasses prepared within the concentration range of x = 0–80 mol% TeO2. The structure of the glasses was studied with a combined Raman, 31P and 11B MAS NMR spectroscopy. 31P MAS NMR and Raman spectrum of the pure 50Li2O-10B2O3-40P2O5 glass indicates the co-existence of Q2 and Q1 phosphate units in the glass structure. Raman spectra of TeO2 containing glasses revealed that TeO2 is incorporated in the structural network in the form of TeO3 and TeO4 (TeO3+1) units. The ratio of TeO4/TeO3 increases with rising TeO2 content. Apart from the formation of P‒O‒Te and Te‒O‒Te bonds, the formation of B‒O‒Te bonds in the form of mixed tetrahedral units B(OP)4-n(OTe)n also takes place as shown by 11B MAS NMR spectroscopy. The structural studies were correlated with the thermal behavior and physical properties of glasses (density, molar volume, chemical durability and refractive index). DSC studies showed that all glasses crystallize on heating within a temperature region of 400–550 °C and the surface nucleation mechanism prevails over the internal one. The crystallization temperature decreases with increasing TeO2 content. The compounds formed by crystallization were LiPO3, Li4P2O7, BPO4 and α-TeO2. Glass transition temperature and dilatometric softening temperature, estimated from thermodilatometry curves, decrease with increasing TeO2 content, whereas the thermal expansion coefficient increases.

Дослідження термічних властивостей захисних літійалюмосилікатних склокерамічних матеріалів

Проаналізовано основні напрямки розробок літійалюмосилікатних склокерамічних матеріалів та встановлено перспективність впровадження у військовій галузі в якості захисних термостійких бронеелементів, які експлуатуються в умовах високошвидкісних механічних навантажень та дії високої температури. Метою даної науково-практичної роботи є дослідження термічних властивостей літійалюмосилікатних склокерамічних матеріалів. Досліджено вплив структури розроблених склокерамічних матеріалів на їх температурний коефіцієнт лінійного розширення та встановлено визначальний вплив фазового складу на термічні властивості. Розроблено модельні літійалюмосилікатні стекла та синтезовано склокерамічні матеріали на їх основі.
 Встановлено, що визначальним фактором при визначенні впливу фазового складу на температурний коефіцієнт лінійного розширення дослідних матеріалів є наявність та вміст β-сподумену у їх складі. Застосування як елементів індивідуального бронезахисту розроблених склокристалічних матеріалів дозволить знизити термоудар, який виникає при зіткненні снаряду з бронематеріалом, що дозволить їх застосовувати в якості матеріалів для бронеелементів.

The effect of mixed alkali on structural changes and ionic migration characteristics in zinc borate glasses

The effect of mixed alkali on structural changes and ionic migration characteristics have been investigated in zinc borate glasses system with composition 5Al2O3-15ZnO-(15-x)K2O-xNa2O-65B2O3(x = 0,3,6,9,12,15mol%). The thermal properties including glass transition temperature (Tg), thermal expansion coefficient (α) and dilatometric softening temperature (Td) were determined by differential scanning calorimeter (DSC) and dilatometer. The ionic migration characteristics were investigated through dc conductivity and chemical stability, determined by electrochemical workstation and normalized mass losses (N(i)). And the glass structure was characterized by Fourier transform infrared spectroscopy, to explain the relationship between structure and properties. As the ratio of [Na2O]/([K2O]+[Na2O])(mol/mol) increase, the glass transition temperature (Tg), dilatometric softening temperature (Td), dc conductivity(σdc) and normalized mass losses (N(i)) of glass exhibit a nonlinear variation, deviate negatively from linearity, meanwhile thermal expansion coefficient (α) varies nonlinearly and deviates positively from linearity. From the FTIR studies the N4 values (fraction of tetrahedral coordinated boron atoms) exhibit a nonlinear variation, deviates negatively from linearity. These data clearly indicated the presence of strong mixed alkali effect (MAE) in the zinc borate glass system, and the MAE changes glass structure and inhibits ion migration.

Effect of Y2O3 content on the crystallization behaviors and physical properties of glasses based on MgO-Al2O3-SiO2 system

Different concentrations of Y2O3 doped MgO-Al2O3-SiO2 system glasses were prepared by melting method. The effects of Y2O3 content on the physical properties, crystallizability, and the resultant microstructures of the glass samples were investigated. With the increase of Y2O3 content, the glass transition temperature, dilatometric softening temperature and micro hardness all increased. Low concentrations of Y2O3 (0–1.0 mol%) favored the formation of quartz solid solution at 840 °C for 1.5 h, and phase transformation from β- to α-quartz solid solution happened after heat treatment at 1000 °C with subsequent cooling process. While high concentration of Y2O3 (1.5 mol%) inhibited the crystallization process, and quartz solid solution formed at a high temperature ~ 940 °C. The phase transformation from β- to α-quartz solid solution happened after heat treatment at 1060 °C with subsequent cooling process. Average crystal sizes were increased significantly with the crystallization temperature increasing from 940 °C to 1120 °C. The coefficient of thermal expansion of the glass treated at 1120 °C decreased obviously around temperature ~ 300 °C, which indicated that the phase transformation from α- to β-quartz solid solution happened in the heating process.