Effect of Ta2O5 Substituting on Thermal and Optical Properties of High Refractive Index La2O3–Nb2O5 Glass System Prepared by Aerodynamic Levitation Method

High refractive index glasses with nominal composition of 0.35La₂O₃–(0.65?x)Nb₂O₅–xTa₂O₅ (x ≤ 0.35) were prepared by aerodynamic levitation method. The effect of Ta₂O₅ substituting on their thermal and optical properties was investigated. All the glasses obtained were colorless and transparent. Differential thermal analyzer results show that as the content of Ta₂O₅ increased, the thermal stability of the glasses increased but the glass‐forming ability decreased. The transmittance spectra of all the obtained glasses exhibited a wide transmittance window ranging from 380 to 5500 nm. As the content of Ta₂O₅ increased, the refractive index of the glasses was enhanced from 2.15 to 2.21 and the dispersion was reduced with the Abbe number increasing from 20 to 27.     

Understanding the structure,thermal, and optical properties in Al2O3-incorporated La2O3-TiO2-Nb2O5 glasses

Glasses in the 30La₂O₃-40TiO₂-30Nb₂O₅ system are known to have excellent optical properties such as refractive indices over 2.25 and wide transmittance within the visible to mid-infrared (MIR) region. However, titanoniobate glasses also tend to crystallize easily, significantly limiting their applications in optical glasses due to processing challenges. Therefore, the 30La₂O₃-40TiO₂-(30−x) Nb₂O₅-xAl₂O₃ (LTNA) glass system was successfully synthesized using a aerodynamic containerless technique, which improves glass thermal stability and expands the glass-forming region. The effects of Al₂O₃ on the structure, thermal, and optical properties of base composition glasses were investigated by XRD, DSC, NMR, Raman spectroscopy, and optical measurements. DSC results indicated that as the content of Al₂O₃ increased, the thermal stability of the glasses and glass-forming ability increased, as the 30La₂O₃-40TiO₂-25Nb₂O₅-5Al₂O₃ (Nb-Al-5) glass obtained the highest ΔT value (103.5°C). Structural analysis indicates that the proportion of [AlO₄] units increases gradually and participates in the glass network structure to increase connectivity, promoting more oxygen to become bridging oxygen and form [AlO₄] tetrahedral linkages to [TiO₅] and [NbO₆] groups. The refractive index values of amorphous glasses remained above 2.1 upon Al₂O₃ substitution, and a transmittance exceeding 65% in the visible and mid-infrared range. The crystallization activation energies of 30La₂O₃-40TiO₂-30Nb₂O₅ (Nb-Al-0) and Nb-Al-5 glasses were calculated to be 611.7 and 561.4 kJ/mol, and the Avrami parameters are 5.28 and 4.96, respectively. These results are useful to design new optical glass with good thermal stability, high refractive index and low wavelength dispersion for optical applications such as lenses, endoscopes, mini size lasers, and optical couplers.     

Thermal Stability,Optical Transmittance,and Refractive Index Dispersion of La2O3–Nb2O5–Al2O3 Glasses

La₂O₃–Nb₂O₅–Al₂O₃ high‐refractive‐index glasses were fabricated by containerless processing, and the glass‐forming region was determined. The thermal stability, density, optical transmittance, and the refractive index dispersion of these glasses were investigated. All the glasses were colorless and transparent in the visible to near infrared (NIR) region and had high refractive index with low wavelength dispersion. Some of these glasses were found to have significantly high glass‐forming ability. These results indicate that the ternary glasses are suitable for optical applications in the visible to NIR region. The effects of the substitution of Al₂O₃ for Nb₂O₅ on optical properties were discussed on the basis of the Drude–Voigt equation. It was suggested that the substitution of Al₂O₃ for Nb₂O₅ increased the molecular density and suppressed a decrease in the refractive index, even when both the average oscillator strength and inherent absorption wavelength decreased in La₂O₃–Nb₂O₅–Al₂O₃ glasses. These results are helpful for designing new optical glasses controlled to have a higher refractive index and lower wavelength dispersion.     

Thermal and optical properties of La2O3–Ga2O3– (Nb2O5 or Ta2O5) ternary glasses

La₂O₃–Ga₂O₃–M₂O₅ (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb₂O₅ and Ta₂O₅ drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga₂O₃ with Nb₂O₅, and the decrease in the Abbe number was significantly suppressed when Ta₂O₅ was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La₂O₃–Ga₂O₃–Ta₂O₅ glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.     

Coloration and Nonlinear Optical Properties of ZnTe Quantum Dots in ZnO–TeO2–P2O5 Glasses

ZnO–TeO₂–P₂O₅ glasses were prepared by melt‐quenching method. The color of the glass samples changed from colorless to pale red and dark red with increasing TeO₂ content. Coloration mechanism and nonlinear optical properties of ZnO–TeO₂–P₂O₅ glasses have been investigated. Raman spectra and transmission electron microscope measurements indicated the precipitation of ZnTe quantum dots in the glasses and ZnTe quantum dots are the origin of coloration. Z‐scan technique was used to examine the nonlinear optical properties of the glasses. The glass sample with 30 mol% TeO₂ exhibits large third‐order nonlinear optical susceptibility of 10^?11 esu.     

New calcium‐free Na2O–Al2O3–P2O5 bioactive glasses with potential applications in bone tissue engineering

Sodium aluminophosphate glasses were evaluated for their bone repair ability. The glasses belonging to the system 45Na₂O–xAl₂O₃‐(55‐x)P₂O₅, with x = (3, 5, 7, 10 mol%) were prepared by a melt‐quenching method. We assessed the effect of Al₂O₃ content on the properties of Na₂O–Al₂O₃–P₂O₅ (NAP) glasses, which were characterized by density measurements, DSC analyses, solubility, bioactivity in simulated body fluid and cytocompatibility with MG‐63 cells. To the best of our knowledge, this is the first investigation of calcium‐free Na₂O–Al₂O₃–P₂O₅ system glasses as bioactive materials for bone tissue engineering.     

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.     

Correlation Between Crystallization Behavior and Network Structure in GeS2–Ga2S3–CsI Chalcogenide Glasses

Diagram of the phase transformation behavior of GeS₂–Ga₂S₃–CsI glasses is realized in this article and the structure‐property dependence of the chalcogenide glasses is elucidated using differential scanning calorimetry and Raman spectroscopy. We observe the compositional threshold of crystallization behavior locates at x = 6–7 mol% in (100?x)(0.8GeS₂–0.2Ga₂S₃)–xCsI glasses, which is confirmed by the thermodynamic studies. Structural motifs are derived from the Raman result that [Ge(Ga)S₄], [S₂GeI₂], [S₃GaI], and [S₃Ga–GaS₃] were identified to exist in this glass network. Combined with the information of structural threshold, local arrangement of these structural motifs is proposed to explain all the experimental observations, which provides a new way to understand the correlation between crystallization behavior and network structure in chalcogenide glasses.     

Y3Al5O12–SiO2 Glasses: Structure and Polyamorphism

Aerodynamic levitation and CO₂ laser melting have been used to synthesize the yttrium aluminosilicate glasses zY₂O₃–yAl₂O₃–xSiO₂ with z/y = 3/5 corresponding to the YAG (Y₃Al₅O₁₂) composition and x between ~5 and ~45 mol%. The low‐ and high‐density (LDA inclusion and HDA matrix) polyamorphic phases in glasses with less than ~14 mol% SiO₂ were identified with backscattering electron imaging. Polarized and depolarized Raman spectra show the formation of various Qⁿ SiO₄ species whose relative populations change smoothly as the SiO₂ content is altered. The AlOs (s = 4–6) and YOz (z = 6–9) polyhedra formed in the YAG glass are preserved upon silica additions while the terminal oxygens of the Q²AlO₄ tetrahedra are gradually bridged to the Qⁿ‐SiO₄ species. The low‐frequency Boson Peak overlaps with the vibrational spectrum and its maximum is redshifted with increasing silica content. Micro‐Raman spectra measured for the LDA and HDA amorphous phases are found to be similar to the spectra of the bulk glass indicating common structural characteristics. The stability of the LDA phase against crystallization appears to be lower than that of the HDA phase. The crystallinity on certain inclusions consisted of YAG microcrystals and a new unidentified microcrystalline phase within Y₄Al_2(1?x)Si_2xO_(9+x) solid solution.     

Effect of TiO2 on microphase development during phase separation and crystallization in Na2O–B2O3–SiO2 glass system

This study examines the incorporation of TiO₂ into sodium borosilicate glasses and its effect on the formation of glassy and crystalline microphases. Glasses in the composition range: 7Na₂O–23B₂O₃–(70 - X)SiO₂–XTiO₂ (where X = 0–14.6 mol.% TiO₂) which exhibit phase separation were investigated. Raman studies confirm the formation of two different TiO₂ coordinations depending on the molar content of TiO₂. Thermal properties of glasses are unaffected by TiO₂ addition. The domain size of microphase development in TiO₂-containing glass indicates competition between phase separation and crystallization. Enrichment of titanium on the interphase between glassy microphases reduces the mass transfer and consequently limits the growth rate of glassy phases. This competes with the formation of anatase for which a nucleation-controlled mechanism is proposed.     

Impact of TeO2–B2O3 manipulation on physical,structural, optical and radiation shielding properties of Ho/Yb codoped mixed glass former borotellurite glass

In this work, (75-x)B₂O₃-xTeO₂-11Bi₂O₃–10Li₂O-1Ho₂O₃-3Yb₂O₃ (x = 10–60 mol%) mixed glass former (MGF) glasses were prepared by using the melt-quenching method to investigate the effect of mixed glass former between B₂O₃ and TeO₂ on the structural, optical and radiation shielding properties of glass. The amorphous nature of the glass samples was confirmed through XRD measurement. Optical ultraviolet–visible light (UV–Vis) spectroscopy revealed that the direct and indirect optical band gap (E_opt) decreased as TeO₂ content increased except for the anomaly at x = 30 mol% due to the interchanging dominance of bridging oxygen (BO) and non-bridging oxygen (NBO) in the glass network. Both direct and indirect refractive indices, n posted an increment except for x = 30 mol% due to polarizability influence of BO and NBO. Urbach energy, E_u declined thus indicating lesser disorder and less defects on the glass structure. The radiation shielding properties of the glass samples were determined for 15 keV–15 MeV photon energy range by using Phy-X/PSD software. Atomic number-dependent parameters such as mass attenuation coefficient (MAC) and effective atomic number (Z_eff) demonstrated an enhanced performances caused by higher Z of Te over B. Meanwhile, density-dependent parameters such as linear attenuation coefficient (LAC), mean-free path (MFP), half-value layer (HVL) and tenth-value layer (TVL) all exhibited an improvement over TeO₂ concentration due to higher density data obtained.     

Microwave Dielectric Properties and Thermally Stimulated Depolarization Currents Study of (1−x)Ba0.6Sr0.4La4Ti4O15–xTiO2 Ceramics

Microwave dielectric properties and thermally stimulated depolarization currents (TSDC) of (1?x)Ba_0.6Sr_0.4La₄Ti₄O₁₅–xTiO₂ (x = 0, 0.01, 0.02, 0.05, and 0.1) ceramics were studied. X‐ray diffraction analysis indicates that the specimens show a hexagonal perovskite structure; however, with an increase of x to 0.1, TiO_2?δ as a secondary phase can be detected in the ceramics. The variation of TiO₂ content has a significant effect on the dielectric properties of (1?x)Ba_0.6Sr_0.4La₄Ti₄O₁₅–xTiO₂ at microwave frequency. The dielectric permittivity of ceramics increases from 44 to 49 with the increase of TiO₂ content. The Qf value is in the range of 39 300–53 400 GHz. However, the temperature coefficient of resonant frequency (τ_f) changes from ?7.5 to–9.4 ppm/°C, and then turns to +3.9 ppm/°C. A near zero τ_f value can be obtained by tuning the content of TiO₂ addition. TSDC was also employed to analysis the extrinsic loss mechanism. Utilizing a fixed polarization condition, the TSDC relaxation peaks are present, which are generated by oxygen vacancies. And the concentration of oxygen vacancies increases with the increase of TiO₂ content. It can be concluded that the extrinsic dielectric loss is dominated by microstructure and oxygen vacancy defects.     

Synthesis and properties of tellurite based glasses containing Na2O,BaO, and TiO2: Raman,UV and neutron/charged particle shielding assessments

In this paper, 75TeO₂–5Na₂O–20BaO?xTiO₂ (TNB-Tix with x = 0, 05, 10, and 15) glasses were synthesized by the conventional melt-quench technique using analytic grade tellurium oxide (TeO₂), barium carbonate (BaCO₃), sodium carbonate (Na₂CO₃) and titanium oxide (TiO₂) as starting chemicals. The prepared glasses were studied for their physical features, Raman and UV spectra, and shielding performance against neutrons and charged particles. The optical property was investigated by UV–Vis spectrometry while the structural evolution of the glasses was studied through the Rahman spectra. Charged particles, slow and fast neutrons interaction parameters of the glasses were calculated theoretically and analyzed as well. The prepared glasses were yellowish without any flaws. The mass density of the glasses increased from 5.1 to 5.4 g/cm³ as TiO₂ content declined from 15 to 0 mol%. Also, an improvement in the optical bandgap from 2.89 to 3.2 eV was recorded as BaO content increased concerning TiO₂ while the refractive index declined from 2.43 to 2.35. Generally, the improvement in the TiO₂ content of the glasses produced a rise in the total and scattering cross section of thermal and slow neutrons respectively. In addition, the fast neutron cross section was enhanced from 0.1005 to 0.1015 cm^?1 for TNB-Ti00 – TNB-Ti15 glasses. The charged particle shielding parameters showed a strong dependence on the chemical structure of the glass system. The present glass system displayed good properties that could make them useful in optical and shielding applications.     

Low‐Temperature Sintering and Microwave Dielectric Properties of ZnNb2O6–TiO2 Ceramics with BaCu(B2O5) Additions

The influence of BaCu(B₂O₅) (BCB) on densification, phases, microstructure and microwave dielectric properties of ZnNb₂O₆–xTiO₂ (x = 1.70–1.90) composite ceramics have been investigated. Undoped ZnNb₂O₆–1.8TiO₂ ceramics sintered at 1200°C exhibit temperature coefficient of resonant frequency (τ_f) ~9.25 ppm/°C. When BaCu(B₂O₅) was added, the sintering temperature of the ZnNb₂O₆–1.8TiO₂ composite ceramics was effectively reduced to 950°C. The results indicated that the permittivity and Q × f were dependent on the sintering temperature and the amounts of BaCu(B₂O₅). Addition of 3.0 wt% BaCu(B₂O₅) in ZnNb₂O₆–1.8TiO₂ ceramics sintered at 950°C showed excellent dielectric properties of ε_r = 40.9, Q × f = 12,200 GHz (f = 5.015 GHz) and τ_f = +0.3 ppm/°C.     

Frequency and Temperature‐Independent Electrical Transport Properties of 2BaO–0.5Na2O–2.5Nb2O5–4.5B2O3 Glass‐Ceramics

The temperature (300–973 K) and frequency (100 Hz–10 MHz) response of the dielectric and impedance characteristics of 2BaO‐0.5Na₂O–2.5Nb₂O₅–4.5B₂O₃ glasses and glass nanocrystal composites were studied. The dielectric constant of the glass was found to be almost independent of frequency (100 Hz–10 MHz) and temperature (300–600 K). The temperature coefficient of dielectric constant was 8 ± 3 ppm/K in the 300–600 K temperature range. The relaxation and conduction phenomena were rationalized using modulus formalism and universal AC conductivity exponential power law, respectively. The observed relaxation behavior was found to be thermally activated. The complex impedance data were fitted using the least square method. Dispersion of Barium Sodium Niobate (BNN) phase at nanoscale in a glass matrix resulted in the formation of space charge around crystal‐glass interface, leading to a high value of effective dielectric constant especially for the samples heat‐treated at higher temperatures. The fabricated glass nanocrystal composites exhibited P versus E hysteresis loops at room temperature and the remnant polarization (P_r) increased with the increase in crystallite size.     

Structural characterization of TiO2–P2O5–CaO glasses by spectroscopy

The structure of glasses with composition x TiO₂·(65 ? x) P₂O₅·35 CaO (x = 0–30 mol%) has been studied and their glass transition temperature, Raman and NMR spectra have been analysed.For TiO₂-free glass two phosphate species have been identified as Q² and Q³. Increasing TiO₂ content in glass compositions results in the disappearance of the Q³ and Q² species and in the formation of, mainly, pyrophosphate structure, Q¹.In calcium titanophosphate glass with higher TiO₂ content the structure consists of a distorted Ti octahedral linked to pyrophosphate unit through P–O–Ti bonds. In these glass series the structural cohesion increases with TiO₂, although a depolymerization in the original P–O–P network occurs.The study of these glasses and the understanding of their structural characteristics can give a valuable contribution for the clarification of their degradation behaviour namely in biological environments.     

Optimization,structural, optical and magnetic properties of TiO2/CoFe2O4 nanocomposites

Magneto-optical TiO₂/xCoFe₂O₄ nanocomposites having various concentrations of CoFe₂O₄ (x = 2, 4 and 6 wt %) were prepared using facile mechanical mixing. X-ray diffraction was employed for the phase examination and microstructure parameters. X-ray diffraction spectra proved the formation of two separate phases: tetragonal titanium dioxide (TiO₂) and face-centered cubic cobalt iron oxide. The structure was further verified by recognizing the selected area electron diffraction (SAED) pattern recorded by a high-resolution transmission microscope. The optical investigation of the prepared nanocomposites verified that the optical band gap values varied from 3.1 eV for pure TiO₂ to 3.05 eV for TiO₂/CoFe₂O₄ (6 wt %). The refractive index, optical dielectric constant and loss factor were discussed in detail. The nanocomposites (TiO₂/xCoFe₂O₄) demonstrated ferromagnetic characteristics and their magnetic parameters were affected by the CoFe₂O₄ percentage in the composites. The sample x = 2 wt % depicted the maximum magnetic exchange bias at room temperature. Moreover, it showed maximum coercivity (H_C) and magnetic squareness ratio (SQ), which makes it suitable for spintronic applications.     

Defective Y2O3−x–driven anomalous photocatalytic enhancement using Y2O3−x–TiO2−x nanorod composite composition spreads

Synergistic photocatalysis is reported, using the optimal amounts of oxygen vacancies of high‐k materials and nanoarchitecture maneuvering by employing a combinatorial sputtering approach. The highlights include (i) the successful fabrication of samples using combinatorial sputtering; (ii) a systematic investigation of the coupling effect between Y₂O_3?x and TiO_2?x; (iii) elucidating charge carrier transport through current‐voltage (I‐V) and capacitance‐voltage (C‐V) characterizations; and (iv) providing an alternative application for high‐dielectric constant (high‐k) materials in photocatalysis. The simple yet effective composition spread technique rapidly determined that Sample 6 (4 at% Y₂O_3?x‐96 at% TiO_2?x, TiO_2?x‐rich on the Y₂O_3?x–TiO_2?x nanorod composite composition spread) exhibited the highest photocatalytic efficiency (i.e., approximately 3.4 times and 1.4 times higher than that of P25 and pure TiO_2?x nanorods, respectively). The predominant factor was determined to be electron migration along defective Y₂O_3?x nanorods to the sample surface. The extracted mobility was discovered to be an order of magnitude greater than that of pure TiO_2?x. The photoelectrochemical stability and reusability were also demonstrated.     

Glass Formation and Ionic Conduction Behavior in GeSe2–Ga2Se3–NaI Chalcogenide System

Series of glassy and glass‐ceramic samples in the GeSe₂–Ga₂Se₃–NaI system is prepared by melt‐quenching technique and the glass‐forming region is well‐defined by XRD investigations. Na‐ion conduction behavior is systemically studied by impedance measurements. For the glasses in the series (100?2x)GeSe₂–xGa₂Se₃–xNaI, ionic conductivities increased with increasing x, whereas the attributed activation energy of ion conduction decreases. The enhanced mechanism is discussed by employing Raman spectra. In addition, the effect of the crystal phases NaI and Ga₂Se₃ on the ionic conduction behavior in the (70?x)GeSe₂–xGa₂Se₃–30NaI samples is discussed. Although it shows that the poorly conducting crystallites of NaI and Ga₂Se₃ have a negative effect on the ionic conductivities in this series, the highest ionic conductivity of 1.65 × 10^?6 S/cm is obtained in the 45GeSe₂–25Ga₂Se₃–30NaI glass. Finally, this study also demonstrates a possible way to search appropriate Na‐ion solid electrolytes for all‐solid‐state batteries.     

Fabrication of Sr0.5Ba0.5Nb2O6 Nanocrystallite‐Precipitated Transparent Phosphate Glass‐Ceramics

Transparent (Sr_0.5Ba_0.5)Nb₂O₆ (SBN50) nanocrystallite‐precipitated phosphate glass‐ceramics were prepared by a conventional glass‐ceramic process. x(SrO–BaO–2Nb₂O₅) ? (100–4x)P₂O₅ (xSBNP) glasses with a refractive index of 1.9–2.0 exhibited high water resistance owing to the presence of Q⁰ and Q¹ phosphate units. Both bulk and surface crystallization of the SBN50 phase were observed in 20SBNP and 21SBNP glass‐ceramics. Although the nominal content of SBN50 crystals in the 21SBNP glass was larger than that in the 20SBNP glass, the latter exhibited better crystallinity of SBN50 and a higher number density of precipitated SBN nanocrystallites. By tuning the two‐step heat‐treatment and the chemical composition, transparent SBN50‐precipitated glass‐ceramics were successfully obtained. Given that no remarkable increase of the relative dielectric constants was observed after crystallization of the SBN50 nanocrystallites, it is postulated that the relative dielectric constant of the bulk is mainly governed by the amorphous phosphate region, and that the contribution of precipitation of the SBN50 nanocrystallites to the dielectric constant is not very significant in this system.