Silica-free sealing glass for sodium-beta alumina battery

A CaO-Bi₂O₃-Al₂O₃-B₂O₃ glass system was studied as a sealant for sodium-sulfur battery. The thermal properties such as thermal expansion coefficient, glass transition, and softening temperature were determined by dilatometry and differential scanning calorimetry. Selected glasses, based on the thermal properties, were bonded with α-alumina substrate followed by aging in air at 400°C for 100 hours and in sodium vapor at 350°C for 100 hours. The interfacial compatibility and resistance to sodium vapor corrosion of the bonded and aged samples were evaluated by structural and microstructural analysis using X-ray diffractometer (XRD) and scanning electron microscope (SEM) attached with energy dispersive spectroscope (EDS). Helium leakage test was performed at room temperature to examine the sealing ability of the select glass. It is found that Bi₂O₃ increases the thermal expansion coefficient, decreases the glass transition and softening temperature, shows excellent interfacial compatibility and thermal cycling resistance, improves sealing ability, and degrades sodium corrosion resistance.     

Comparison between barium and strontium-glass composites for sealing SOFCs

The present study demonstrates the feasibility of adding micron-scale Y₂O₃-stabilized ZrO₂ (YSZ) powders to modify the properties of two borate glasses used for sealing electrolyte supported SOFCs. The crystallization of the composite made with a Ba-containing glass was found to be independent of the volume fraction of YSZ, as opposed to the situation for Sr-glass composites where the crystallization temperature decreased with the volume fraction of YSZ. The variation of the flow properties of both glass composites was measured using a wettability test, and an increase of the contact angle was measured when the volume fraction of additives was increased. Examining the microstructure showed that initially the Ba-containing glass reacted with YSZ to form a BaZrO₃ compound. Long time exposure at 800 °C caused a large reduction of the coefficient of thermal expansion (CTE), which is explained by increased formation of BaZrO₃ and further change in glass composition. On the other hand, the reaction involving the Sr-containing glass with the YSZ additive shows the initial formation of calcium zirconate (Ca is an ingredient in both glasses) followed by appearance of strontium zirconate with further heating. For this Sr glass composition, the observed reduction of CTE was associated with the change in composition of the remaining glassy phase since the CTEs of the reaction products are close to the CTE of the YSZ additives.     

Sealing Glass‐Ceramics with Near Linear Thermal Strain,Part I: Process Development and Phase Identification

A widely adopted approach to form matched seals in metals having high coefficient of thermal expansion (CTE), e.g. stainless steel, is the use of high CTE glass‐ceramics. With the nucleation and growth of Cristobalite as the main high‐expansion crystalline phase, the CTE of recrystallizable lithium silicate Li₂O–SiO₂–Al₂O₃–K₂O–B₂O₃–P₂O₅–ZnO glass‐ceramic can approach 18 ppm/°C, matching closely to the 18 ppm/°C–20 ppm/°C CTE of 304L stainless steel. However, a large volume change induced by the α‐β inversion between the low‐ and high‐ Cristobalite, a 1^st order displacive phase transition, results in a nonlinear step‐like change in the thermal strain of glass‐ceramics. The sudden change in the thermal strain causes a substantial transient mismatch between the glass‐ceramic and stainless steel. In this study, we developed new thermal profiles based on the SiO₂ phase diagram to crystallize both Quartz and Cristobalite as high expansion crystalline phases in the glass‐ceramics. A key step in the thermal profile is the rapid cooling of glass‐ceramic from the peak sealing temperature to suppress crystallization of Cristobalite. The rapid cooling of the glass‐ceramic to an initial lower hold temperature is conducive to Quartz crystallization. After Quartz formation, a subsequent crystallization of Cristobalite is performed at a higher hold temperature. Quantitative X‐ray diffraction analysis of a series of quenched glass‐ceramic samples clearly revealed the sequence of crystallization in the new thermal profile. The coexistence of two significantly reduced volume changes, one at ~220°C from Cristobalite inversion and the other at ~470°C from Quartz inversion, greatly improves the linearity of the thermal strains of the glass‐ceramics, and is expected to improve the thermal strain match between glass‐ceramics and stainless steel over the sealing cycle.     

Gel-derived SiO2–CaO–P2O5 bioactive glasses and glass-ceramics modified by SrO addition

The effect of SrO substitution for CaO in two sol–gel glasses with different chemical compositions (mol%) A2Sr: (54−x)CaO–xSrO–6P₂O₅–40SiO₂ and S2Sr: (16−x)CaO–xSrO–4P₂O₅–80SiO₂ (x=0, 1, 3 and 5) stabilized at 700 °C on their structure (XRD, FTIR) and bioactive properties (SBF test) was investigated. Preliminary in vitro tests using human articular chondrocytes of selected A2Sr glass were also conducted. Moreover, the subject of this study was to detect the changes on material properties after heat treatment at 1300 °C. The results show that the effect of strontium substitution on structure, bioactivity and crystallization after treatment at both the above temperatures strongly depends on CaO/SiO₂ molar ratio. The presence of 3–5 mol% of strontium ions creates more expanded glass structure but does not markedly affect crystallization ability after low temperature treatment. Sintering at 1300 °C of A2 type glasses results in crystallization of pseudowollastonite, hydroxyapatite and also Sr-substituted hydroxyapatite for 3–5 mol% of SrO substitution. The increase of strontium concentration in silica-rich materials after sintering leads to appearance of calcium strontium phosphate instead of calcium phosphate. Bioactivity evaluation indicates that substitution of Sr for Ca delays calcium phosphate formation on the materials surface only in the case of silica-rich glasses treated at 700 °C. Calcium-rich glasses, after both temperature treatments, reveals high bioactivity, while crystal size of hydroxyapatite decreases with increasing Sr content. High temperature treatment of high-silica glasses inhibits their bioactivity. Preliminary in vitro tests shows Sr addition to have a positive effects on human articular chondrocytes proliferation and to inhibit cell matrix biomineralization.     

Crystallization of CaO–MgO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass prepared by float process

CaO–MgO–Al₂O₃–SiO₂ (CMAS) glass was prepared by float process. The effects of TiO₂ and heat-treatment on properties and crystallization behaviors of float glasses were investigated by atomic force microscope, differential scanning calorimeter, X-ray diffraction, electron probe microanalyzer, field emission scanning electron microscope and viscosity test. The results showed that CMAS parent glasses produced by float process had a high surface flatness (Ra is less than 80.1 ± 0.1 nm) and low tin penetration (14 μm). When the concentration of TiO₂ increased from 3.51 to 5.01 wt %, the glass transition temperature was decreased, and the crystallization temperature was shifted from 913 to 887°C using differential scanning calorimeter. Field emission scanning electron microscope images showed that phase separation was discovered in CMAS parent glass (containing 3.51 wt % TiO₂) treated at 670°C. Diopside as a major crystalline phase was precipitated in CMAS glass-ceramics nucleated at 700°C for 30 min and followed by crystallization at 910°C for 30 min.     

Tuning the interfacial reaction between CaO–SrO–Al2O3–B2O3–SiO2 sealing glass–ceramics and Cr-containing interconnect: Crystalline structure vs. glass structure

In this paper, Al₂O₃ was added to CaO–SrO–B₂O₃–SiO₂ sealing system to tailor the structure of sealing glass–ceramics and glass–ceramics/metal interfacial reaction. The addition of alumina in glasses contributes to increasing fraction of bridging oxygen in silica tetrahedral as well as the change in boron environment from three-fold to four-fold (BO₄ → BO₃). The devitrification tendency of glasses also decreases with increasing Al₂O₃ content. The condensed glass structure and increasing residual glass content play opposite roles on the interfacial reaction, consequently resulting in a maximum fraction of Cr⁶⁺ in reaction couples between Cr₂O₃ and glass containing 6 mole% Al₂O₃ at 700 °C. In addition, the good bonding can be observed at the interface between Cr-containing interconnect (Crofer 22APU) and glass containing 4 mole% Al₂O₃, held at 700 °C for 100 h. The reported results support the suitability of the prepared glass–ceramics as sealing materials for SOFC applications.     

Passive filler loaded polysilazane-derived glass/ceramic coating system applied to AISI 441 stainless steel,part 2: Oxidation behavior in synthetic air

This article features the oxidation behavior of ferritic stainless steel grade AISI 441 coated with protective polymer-derived ceramics (PDC). Two PDC compositions are studied with respect to their oxidation resistance in a flow-through atmosphere of synthetic air at temperatures of up to 1000°C. The coatings contain a combination of six passive fillers: Y-containing ZrO₂, glass microspheres, alumina-yttria-zirconia (AYZ) powder, and three commercial glasses. They are pyrolyzed in air for 1 hour at 800°C with heating and cooling rates of 3 K/min. Detailed microstructural examination of the oxide products formed at the surface of samples after exposure to air at 900°C, 950°C, and 1000°C for 1-48 hours is analyzed. Both uncoated steel and steel coated with two of the protective systems described in part 1 of this article are investigated. Fe, Cr₂O₃, TiO₂, and a spinel of the composition (Mn,Cr)₃O₄ are identified at the oxidized surface of the steel substrate using X-ray diffraction. A significant weight gain of the unprotected steel is measured after all experiments, while oxidation tests of the coated steel show a negligible weight gain after 900°C and 950°C. During the early stages of coating oxidation, the monoclinic-to-tetragonal ratio in the zirconia filler is shifted toward the monoclinic modification. Longer exposures and higher temperatures lead to the formation of yttrium aluminum garnet (YAG) due to glass microsphere crystallization and solid state reactions in the AYZ powder. The crystallization of the three commercial glasses functioning as sealants leads to the formation of Ba(AlSiO₄)₂ also known as hexacelsian, which subsequently transforms to celsian. YZr₈O₁₄ is also formed. The protective effect of the PDC coatings applied to the stainless steel is demonstrated up to 950°C.     

Effect of nickel doping on structure and suppressing boron volatility of borosilicate glass sealants in solid oxide fuel cells

The high volatility of boron from borosilicate glass sealants often leads to boron deposition and poisoning of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode, presenting a challenge for the development of reliable solid oxide fuel cells (SOFCs). In this paper, we report that boron volatilization from borosilicate glass at 700 °C can be significantly suppressed by appropriate NiO dopant, mainly due to the increase of Si-O-B linkages in the combining B-O^? and Si-O^? network. Also, the formation of boron-containing phase in NiO-doping glass-ceramics has been studied, which suppresses the reaction between glass and LSCF cathode after heat treatment at 700 °C for 1000 h. Moreover, the change of crystalline phases leads to an improvement in thermal and electrical properties. We believe that our findings will open a new way for the design and development of the reliable sealing glass for SOFCs applications.     

Structural,mechanical, and in vitro characterization of freeze-cast scaffolds prepared using a sol-gel-derived bioactive glass from the SiO2–CaO–Na2O–P2O5–K2O–MgO system

This work deals with the preparation of freeze-cast scaffolds using a bioactive glass from the SiO₂–CaO–Na₂O–P₂O₅–K₂O–MgO system. This material could be sintered at lower temperatures (650 °C) than other variations of bioactive glasses, which is an important advantage in terms of energy and cost savings. This behavior represents a great advantage in terms of energy and cost savings. The freeze-casting step was conducted using water as a solvent and liquid nitrogen as a coolant. The prepared samples were examined according to their pore structure, thermal behavior, mechanical stability, and bioactivity. The glass transition temperature (T_g), crystallization onset temperature (T_x), and maximum crystallization temperature (T_c) evaluated for this bioactive glass were about 660 °C, 690 °C, and 705 °C. Consequently, the freeze-cast scaffolds could be sintered at 650 °C for 2–8 h, which favored viscous flow sintering without crystallization. Bioactivity assays were conducted by soaking the scaffolds in simulated body fluid for up to 21 days, showing that these materials present a bioactive behavior, inducing hydroxyapatite formation. These materials' mechanical properties and biocompatibility make them promising candidates for use in trabecular bone repair.     

Preparation of transparent Bi2O3-ZnO-B2O3 glass by conventional sintering at low temperatures

Glass components fabricated by the sintering route have wide-ranging applications. However, one issue is that the crystallization tendency of glass powders often leads to residual pore-glass interfaces and crystal-glass interfaces, thereby causing strong light scattering and rendering the sintered glass opaque. This issue is particularly pronounced in glasses with a low glass transition temperature (T_g) due to their weak bonding and thus high crystallization tendency. In the present study, a Bi₂O₃-ZnO-B₂O₃ glass with a low T_g of 364°C was fabricated using the conventional sintering method to explore whether transparent glass materials can be obtained. The temperature range of crystallization of the glass powders was analyzed using differential scanning calorimetry. X-ray diffraction was employed to analyze the crystalline phases formed in the sintered glasses. The microstructure of the sintered glasses was examined using scanning electron microscopy. The optical transmittance of the sintered glasses was measured using ultraviolet-visible spectroscopy. The results show that transparent sintered glasses with the highest transmittance of 54% at the wavelength of 650 nm can be obtained by using a coarser initial particle size, lower forming pressure, and an appropriate sintering temperature/time (430°C/30 min). It is suggested that this combination of processing parameters can suppress glass crystallization while maintaining a low glass viscosity during sintering.     

T–T–T behaviour of bioactive glasses 1–98 and 13–93

In this work crystallization kinetics of bioactive glasses 1–98 and 13–93 are discussed. Within a certain temperature–time window these glasses can be hot worked into various products without interfering with crystallization. The crystallization was studied isothermally by heating glass plates at different temperatures for different times. Phases in the samples were studied through XRD and SEM analyses. The nucleation-like curves and crystallization characteristics were measured with DTA. The temperature of maximum nucleation was measured for glass 1–98 at 725 °C and for 13–93 at 700 °C. The activation energy of crystallization of both glasses was 280 kJ/mol. The Johnson–Mehl–Avrami exponent and the SEM micrographs of the samples suggested surface crystallization. The primary crystalline phase was wollastonite. The growth rate of the crystallized surface layer was 1 order of magnitude higher in the plates of 1–98 than in 13–93. The results can be utilized to optimize the parameters in hot-working of the glasses.     

The Kinetics of Melting Crystallization of Poly-L-Lactide

The influence of non-isothermal melt crystallization on thermal behavior and isothermal melt crystallization kinetics of poly-L-lactide (PLLA) were investigated by differential scanning calorimetry (DSC), polarizing micrograph (POM) and x-ray diffraction (XRD). Crystallization performed at lower cooling rates (2°C·min^?1) is accompanied by a variation of the kinetics around 118°C. The glass transition temperature of PLLA decreases with increase of cooling rate, and the crystallinity at the end of crystallization increases with decreasing cooling rate. The size of PLLA spherulites increases with a decrease in the cooling rate, and PLLA becomes almost amorphous cooled at rapid rate (>10°C·min^?1). PLLA exhibits an Avrami crystallization exponent n = 3.01±0.13 in isothermal crystallization in the range from 90°C to 140°C. According to Hoffman-Lauritzen theory, two crystallization regime are identified with a transition temperature occurring at 118°C, and the value of K_g(II)/K_g(III) is 2.17 [K_g(II) = 6.025 × 10⁵K², K_g(III) = 1.307 × 10⁶ K²].     

Preparation and sealing effects of Mg–Al–Si–Ba–O-based glass-ceramic coatings on NTC thermistors

Herein, Mg–Al–Si–Ba–O-based glass ceramics were studied as potential candidates to protect Mn–Co–Ni–O-based negative temperature coefficient (NTC) thermistors at high temperatures such as 900 °C. The ceramics were prepared in three glass formulations (1#: 15MgO–15Al₂O₃-44.7SiO₂–25BaO, 2#: 17MgO–17Al₂O₃–41SiO₂–25BaO and 3#: 17MgO–17Al₂O₃–41SiO₂–20BaO–5Y₂O₃ (in mol%)) and their glass-transition temperatures (T_g) were determined using the differential scanning calorimetry (DSC) method. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the parent glasses and glass-ceramic coatings. The sealing effects of the glass ceramics were examined by conducting an insulation test. The glass-ceramic sealing structures were subjected to 1000 thermal shock cycles at temperatures varying from room temperature to 900 °C. Notably, the sealing structure of glass-ceramic coating 1# was compact at a T_g of 760.9 °C. The glass-ceramic coatings effectively maintained the NTC properties of the sensitive ceramics in all three formulations. Interestingly, the glass-ceramic coating 3# containing Y₂O₃ demonstrated an increase in electrical resistance. Both the NTC thermistors coated with 1# and 2# glass formulations successfully passed 1000 thermal shock cycles without visible failures, and their resistance change ratios were well below the requisite 20%.     

Structural–chemical features and mechanism of crystallization of TlAsX<Subscript>2</Subscript> glasses (X = S,Se)

The vibrational IR spectra of polymer-chain glasses and single crystals of TlAsX₂ (X = S, Se) have been studied. The results of the kinetic study of the surface isothermal crystallization of glasses are theoretically anlayzed in different ways, taking into account the peculiarities of their structure. The semiempirical calculation of the temperature dependence of nonreconstructive crystal growth rate is performed. It is shown that the layered stationary growth of crystals in the TlAsS₂ glass occurs on screw dislocations. In the TlAsSe₂ glass the transition from a dislocation mechanism to two-dimensional nucleation and the layered growth of crystals is possible at supercooling of more than 120°C.     

Evaluation of novel composition (SiO2–CaO–Na2O–P2O5, SrO–CuO) degradable amorphous silicate glasses properties and comprehensive characterization of the thermal features

The current work presents and discusses the findings of a comprehensive study on the structural, chemical and thermal properties of SrO and CuO incorporated SiO₂–CaO–Na₂O–P₂O₅ amorphous silicate glass with a novel composition. Here, fundamental features (experimental density, oxygen density, and hardness) of all glasses were determined and chemical as well as phase composition of the glasses was verified with XRF and XRD, respectively. Moreover, the thermal behavior (viscos flow and crystallization kinetics) of amorphous silicate glass was investigated by non-isothermal methods using DTA analysis. The activation energies of glass transition (E_g) were calculated in the range of 546–1115 kJ/mol by Kissinger method, whereas the activation energies of crystallization (E_c) were calculated in the range of 164–270 kJ/mol by three different methods (Kissinger, Ozawa, Yinnon and Uhlmann). Avrami exponent (n) values ranged from 1.17 to 3.28 demonstrated that amorphous silicate glasses have different crystallization mechanism. Working temperature, which is one of the parameters indicating glass stability, increased with the incorporation of Sr and Cu from 187 °C to 245 °C. The initial dissolution measurement has been applied to study the degradability behavior of Sr and Cu incorporated amorphous glasses in vitro. Quantitative evaluation of Si⁴⁺ (0.156–0.373 kV), Ca²⁺ (0.043–0.332 kV), Na⁺ (0.044–0.329 kV), P⁵⁺ (0.057–0.289 kV), Sr²⁺ (0.134–0.385 kV), and Cu²⁺ (0.090–0.203 kV) depending on the ion activation energy (E_a-ion) and ion concentration at different temperature values (24, 37 and 55 °C) was performed in contact with Tris-HCl solution by ICP-OES analysis. The results revealed that investigated glasses were degradable and incorporation of Sr and Cu affected the glass initial dissolution. Overall, investigated glasses are suitable for various application such as hot-working production, glass-ceramic manufacturing, and glass or glass-ceramic scaffolds fabrication, due to wide working temperature ranges and high crystallization tendencies of the developed glasses.     

Synthesis of glass–ceramics in the CaO–MgO–SiO2 system with B2O3, P2O5, Na2O and CaF2 additives

Glass–ceramics based on the CaO–MgO–SiO₂ system with limited amount of additives (B₂O₃, P₂O₅, Na₂O and CaF₂) were prepared. All the investigated compositions were melted at 1400 °C for 1 h and quenched in air or water to obtain transparent bulk or frit glass, respectively. Raman spectroscopy revealed that the main constituents of the glass network are the silicates Q¹ and Q² units. Scanning electron microscopy (SEM) analysis confirmed liquid–liquid phase separation and that the glasses are prone to surface crystallization. Glass–ceramics were produced via sintering and crystallization of glass-powder compacts made of milled glass-frit (mean particle size 11–15 μm). Densification started at 620–625 °C and was almost complete at 700 °C. Crystallization occurred at temperatures >700 °C. Highly dense and crystalline materials, predominantly composed of diopisde and wollastonite together with small amounts of akermanite and residual glassy phase, were obtained after heat treatment at 750 °C and 800 °C. The glass–ceramics prepared at 800 °C exhibited bending strength of 116–141 MPa, Vickers microhardness of 4.53–4.65 GPa and thermal expansion coefficient (100–500 °C) of 9.4–10.8 × 10⁻⁶ K⁻¹.     

Barium Borosilicate Sealing Glasses Synthesized by a Sol–Gel Process: Chemical Interactions with a Stainless Steel and Gas‐Tightness of a SOFC

Several glasses synthesized by sol–gel route and based on the BaO–B₂O₃–X–Al₂O₃–SiO₂ (X = CaO, MgO) glass system have been investigated to evaluate their applicability as sealant for solid oxide fuel cell (SOFC). Chemical interactions with K41X stainless steel and hydrogen‐tightness of these materials were evaluated after operations at high temperatures over 1,000 h in air atmosphere. Formation of a new phase at the steel–glass interface and formation of porosity in the glass were observed and determined as critical problems over mid‐term operations. The role of MgO is important to obtain a gas‐tight sealing. Application of the glass paste without binder addition was performed in order to avoid possible residual porosity related problems. The best glass was finally used as sealant between anodic and cathodic compartments in complete SOFCs operated at 760 and at 800 °C. Open circuit voltages and power densities of the cells were recorded during the first hours of operation.     

BAS (BaO·Al2O3·SiO2)-glasses for high temperature applications

The paper concerns the commercial BAS (BaO·Al₂O₃·SiO₂)-glass AF45 from the Fa. DESAG, Germany, and reports an investigation to test the suitability as sealing glass for the SOFC. Importantly the crystallization behaviour is characterized. A crystallization of the sealing glasses is necessary to fulfil the high requirements for joining. Samples are screen printed films with addition of MgO. The glass AF45 is a slowly crystallizing glass. In general the crystallization rate can be regulated within wide limits by means of MgO addition.     

Unusual crystallization pathways revealed in six barium disilicate (BaSi2O5) glasses

Due to the unusual crystallization of (nominally) stoichiometric BaSi₂O₅ (BS2) glass, which shows unexpected and diverse crystal phases, a series of six glasses with different chemicals and melting procedures were prepared in three laboratories and characterized before and after crystallization by differential scanning calorimetry, density measurements, X-ray diffraction, FTIR, and Raman spectroscopy. The aim of this study was to assess whether there is systematic behavior in the crystallization pathways in relation to precursor chemicals, impurities, and hydroxyl content of this glass. Small glass monoliths were treated at the first DSC crystallization peak and quenched to determine which phases formed in the early-stages of crystallization. The glass transition temperatures (T_g) divide these six glasses between those with a T_g near 690 °C versus those near 700 °C. The DSC peak crystallization temperatures varied even more; from 855 to 917 °C. In these six glasses, our results are best explained by a combination of metastable high-BaSi₂O₅ and Ba₆Si₁₀O₂₆. Monotonic trends in crystallization show that the DSC signal from the Ba-rich phases increases as the T_g and the crystallization temperatures increase. The BS2 glasses with both the lowest T_g and lowest DSC crystallization temperatures show the most barium disilicate crystal. This leads to the conclusion that the metastable monoclinic high-BaSi₂O₅ is favored in these conditions. The small differences in glass synthesis conditions and chemicals used strongly influence the relative proportions of phases which crystallize and their kinetics. In-situ and ex-situ diffraction measurements confirm the conclusions above. The structural distinctions between the barium silicate crystals and the BS2 supercooled liquid, and the implications for the role of structural polymerization are discussed. We conclude that high-BaSi₂O₅ or Ba₆Si₁₀O₂₆ are the predominant phases in the earliest stages of crystallization. This study highlights the extreme sensitivity of BS2 glass crystallization kinetics and pathways to minor differences in composition and synthesis conditions and explains the different conclusions reached by distinct authors that worked on the crystallization of BS2 glasses.     

Synthesis of glass-ceramics in the Na2O/K2O-CaO-MgO-SiO2-P2O5-CaF2 system as candidate materials for dental applications

This study reports on the sintering behavior, crystallization process, and mechanical properties of novel glass-ceramics (CGs) produced by the glass powder compact consolidation method. Substitution of K₂O for Na₂O and MgO for CaO was attempted in the parent glasses belonging to Na₂O-CaO-MgO-SiO₂-P₂O₅-CaF₂ system. Glass powder compacts were heat treated at various temperatures between 700°C and 900°C, taking under consideration the glass transition (T_g) and the crystallization peak (T_p) temperatures, which were experimentally determined for each investigated glass by thermal analysis (dilatometry and differential scanning calorimetry). The experimental results showed that sintering always preceded crystallization, regardless of the type of substitution. In the case of MgO substitution for CaO, crystallization was advanced in the range of 800°C-850°C, resulting in the formation of an assembly of crystalline phases, such as diopside, fluorapatite, and wollastonite. The substitution of K₂O for Na₂O increased the activation energy for crystallization, shifting crystallization process to a high temperature region, with the formation of alpha-potassium magnesium silicate, instead of wollastonite. The GCs produced had values of 22-31 GPa regarding the modulus of elasticity, 5.0-6.1 GPa concerning the microhardness, and 1.4-1.9 MPa⋅m^0.5 as regard the fracture toughness, which are similar to those of the human jawbone.