ZnO B2O3 Research Articles

Effect of Glass Refractive Index on Light Extraction Efficiency of Light‐Emitting Diodes

Light‐emitting‐diode (LED) encapsulants, such as epoxy and silicone resin, have a lower refractive index than YAG:Ce phosphor, and this is usually one of the major causes of LED inefficiency. To improve LED performance, a glass encapsulant is considered. In this study, the SiO2–B2O3–ZnO glass system containing La2O3 and WO3 was investigated as an encapsulant to minimize total internal reflection and to increase the light extraction efficiency of LED packages. The characterization of glass encapsulants was performed using a differential scanning calorimeter, a pycnometer, a prism coupler, X‐ray photoelectron spectroscopy, and integrating spheres. The refractive index increased linearly with increasing molar volume of glass because La2O3 and WO3 act as modifiers in the glass, creating more nonbridging oxygen. The refractive index of glass increases with the content of La2O3 and WO3, which is attributed to the increase in polarizability of oxide ions in the glass. When the refractive index between glass and phosphor matched, light extraction efficiency was maximized because total internal reflection decreased.

Low temperature sintering and microwave dielectric properties of 0.6Li2ZnTi3O8–0.4Li2TiO3 ceramics doped with ZnO–B2O3–SiO2 glass

The novel low-temperature sinterable 0.6Li2ZnTi3O8–0.4Li2TiO3 ceramics were prepared by cofiring the mixtures of pure-phase Li2ZnTi3O8, Li2TiO3 and ZnO–B2O3–SiO2 glass. Li2ZnTi3O8 and Li2TiO3 phase could well coexist in the sintered samples with no second phase detected. The near-zero temperature coefficients of the resonant frequency (τf) were achieved and simultaneously the desirable quality factor Q×f values could be maintained. Typically, the 0.6Li2ZnTi3O8–0.4Li2TiO3 ceramics with 1.0wt% ZBS addition could be well densified at only 900°C and exhibited excellent microwave dielectric properties of εr=25.4, Q×f=86,400GHz and τf=−1.0ppm/°C, thus showing a great potential as a middle permittivity low-temperature cofired microwave dielectric material.

Effects of the replacing content of ZnBr2 on the properties of ZnO–B2O3–SiO2:Mn2+ glass-ceramics

ZnBr2-doped ZnO–B2O3–SiO2:Mn2+ (ZBSM) optical-storage glass-ceramics were successfully prepared by a sol–gel method. The crystalline phase and microstructure of ZBSM were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The addition of ZnBr2 influenced the crystallization of the ZBSM glass-ceramics. Moreover, the effects of ZnBr2 additive on the preparation of glass-ceramics were analyzed by differential scanning calorimetry. The optical storage properties of the samples were investigated by photoluminescence spectroscopy, long-lasting phosphor (LLP) decay curves, and thermoluminescence (TL) spectroscopy. The LLP decay curves show that the lower phonon energy of Br− ions generates more stable metastable energy. The TL spectra and Gaussian fitting indicate that the sample with 20mol% ZnBr2 content exhibited the best performance.

A new temperature stable microwave dielectric ceramic with low-sintering temperature in Li2TiO3–Li2Zn3Ti4O12 system

The crystalline phases, microstructure, composition analysis and microwave dielectric properties of Li2TiO3–xvol.% Li2Zn3Ti4O12 (x=15–40) composite ceramics with 1–3wt.% Li2O–ZnO–B2O3 (LZB) glass addition prepared by solid-state reaction method have been investigated. A near zero temperature coefficient of resonant frequency (τf) of about −1.3ppm/°C was obtained in the Li2TiO3–30vol.% Li2Zn3Ti4O12 ceramic sintered at 1100°C for 2h with permittivity of 22.0, Q×f value of 38,900GHz. The microwave dielectric properties of Li2TiO3–20vol.% Li2Zn3Ti4O12 ceramics with 1–3wt.% LZB glass addition sintered at 900°C for 2h were characterized. The addition of 2.5wt.% LZB glass reduced the sintering temperature of the Li2TiO3–20vol.% Li2Zn3Ti4O12 ceramic from 1100°C to 900°C without obvious degradation of the microwave dielectric properties. The 2.5wt.% LZB glass-added Li2TiO3–20vol.% Li2Zn3Ti4O12 ceramic sintered at 900°C for 2h could reach a high relative density of 98% of the theoretical density of the Li2TiO3–20vol.% Li2Zn3Ti4O12 ceramic and exhibited microwave dielectric properties of ɛr=22.0, Q×f=28,407GHz, and a near zero τf value of −1.6ppm/°C. Moreover, this ceramic has a chemical compatibility with Ag electrode, making it a very promising candidate material for Low-temperature co-fired ceramic (LTCC) applications.

The chemical inertness of Ir–Re and Ta–Ru coatings in molding B2O3–ZnO–La2O3-based glass

B2O3–ZnO–La2O3-based glasses with a high refractive index are widely used as optical glass materials for lenses. To evaluate the feasibility of applying protective coatings on glass molding dies, Ir–Re and Ta–Ru coatings were sputtered on cemented tungsten carbide or silicon substrates. B2O3–ZnO–La2O3-based glasses were placed on the surface of the coatings and heat-treated in a glass molding atmosphere of 15-ppm O2–N2 at a molding temperature of 600°C. Up to 1000 thermal cycling annealing tests were performed at 270°C and 600°C. The holding time at the molding temperature was set at 1min for each cycle. The variations in chemical inertness, residual stress, and coating characteristics after annealing were investigated.

Effects of lanthanum oxide on the properties of barium-free alkaline-earth borosilicate sealant glass

We have explored the effects of lanthanum oxide (La2O3) on the properties of barium-free SrO–CaO–ZnO–B2O3–SiO2 glass system varying its content from 0 to 6mol%. The coefficient of thermal expansion and glass transition temperature of the glasses are found to be in the ranges 10.6–10.8×10−6/K (50–600°C) and 650–690°C respectively. Differential scanning calorimetric studies revealed an increase in crystallization peak temperature and thermal stability of the glasses up to 4mol% and then decrease on further addition. A monotonic increase in characteristic shrinkage temperature of glass powder compact is observed on addition of La2O3 as revealed in the heating stage microscopic study. X-ray diffraction studies revealed reduced crystallization peak intensity in La2O3 added glasses. Fourier transformed infrared spectra disclosed that the addition of La2O3 stabilized the glass structure by reducing the number of non-bridging oxygens. Vickers micro hardness of the glasses varied in the range 2.6–5.6GPa. Scanning electron microscopy revealed the formation of particulate nature of microstructures in parent glass which is not observed in the La2O3 added glasses. Activation energy of crystallization has increased from 331 to 361kJ/mol determined by Kissinger and Augis–Bennett models. Above properties of these glasses clearly advocate their applicability as solid oxide fuel cell sealants.

Fabrication of transparent sintered ZnO-B2O3-Bi2O3 glass body by pressureless firing and hot isostatic pressing

The optimum conditions for the fabrication of transparent glass body in the ZnO-B2O3 (ZB) and ZnO-B2O3-Bi2O3 (ZBB) systems were examined by a pressureless firing and subsequent oxygen-supplied hot isostatic pressing (HIP). The pressurelessly-fired opaque ZB glass body possessed the maximum relative density (99.1%) when fired at 620°C for 15 min in air, and was hot isostatically pressed at 630°C for 12 h under the pressure of 150MPa (80%Ar – 20%O2 atmosphere) to eliminate the residual pores; the light transmittance of this glass body was in the range of 35 to 51% (380 to 800 nm). In order to fabricate the transparent glass body at lower temperature, the fabrication conditions of ZBB glass body were examined. The pressurelessly-fired ZBB glass body possessed a maximum relative density (98.8%) when fired at 500°C for 2 h in O2 atmosphere and hot isostatically pressed at 490°C for 12 h; the transmittance of the transparent ZBB glass body was in the range of 48 to 58% (500 to 800 nm).

Low temperature cofirable Li2Zn3Ti4O12 microwave dielectric ceramic with Li2O–ZnO–B2O3 glass additive

The effects of Li2O–ZnO–B2O3 (LZB) glass additive on the sintering behavior, phase composition, microstructure and microwave dielectric properties of Li2Zn3Ti4O12 ceramics were investigated. The addition of a small amount of LZB glass can reduce the sintering temperature of Li2Zn3Ti4O12 ceramics from 1,075 to 900 °C without much degradation of the microwave dielectric properties. Only a single-phase Li2Zn3Ti4O12 is formed in Li2Zn3Ti4O12 ceramic with LZB addition. Typically, the 1.5 wt% LZB glass-added Li2Zn3Ti4O12 ceramic sintered at 900 °C for 2 h can reach a high relative density of 97.5 % and exhibits good microwave dielectric properties, i.e., relative dielectric constant (e r ) = 19.1, quality factor (Q) = 7083.5 at 9 GHz, and temperature coefficient of resonant frequency (τ f ) = − 48.9 ppm/°C. In addition, the ceramic could be co-fired well with an Ag electrode, which is made it as a promising dielectric ceramic for low temperature co-fired ceramics technology application.

Low‐Fire Processing of MicrowaveBNBT‐Based High‐k Dielectric withLi2O–ZnO–B2O3Glass

The effects ofLi2O–ZnO–B2O3(LZB) glass addition on densification and dielectric properties ofBa4(Nd0.85Bi0.15)9.33Ti18O54(BNBT) have been investigated. At a given ratio ofZnO/B2O3, the glass softening point decreases, but the thermal expansion coefficient and dielectric constant increase with increasingLi2Ocontent in theLZBglass. With 10 vol%LZBglass, the densification temperature reduces greatly from 1300°C for pureBNBTto 875°C–900°C forBNBT + LZBdielectric, and the densification enhancement becomes more significant with increasingLi2Ocontent in theLZBglass. The above result is attributed to a chemical reaction taking place at the interface ofLZB/BNBTduring firing, which becomes less extensive with increasingLi2Ocontent in theLZBglass. Therefore, more residualLZBglass, which acts as a densification promoter toBNBT, is left with increasingLi2Ocontent. For theLZBglass with aLi2Ocontent in the range 10–30 mol%, the resulting 90 vol%BNBT + 10 vol%LZBmicrowave dielectric has a dielectric constant of 55–70, product (Q × fr) of quality factor (Q) and resonant frequency (fr) of 1000–3000 GHz at 5–5.79 GHz, and a temperature coefficient of resonant frequency (τf) of 10–60 ppm/°C in the temperature range between 25°C and 80°C.

Effect of the Molar Ratio of B2O3 to Bi2O3 in Al Paste with Bi2O3–B2O3–ZnO Glass on Screen Printed Contact Formation and Si Solar Cell Performance

In this study, eco-friendly Pb-free Bi2O3–B2O3–ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3 to B2O3 in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3 to B2O3 increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3 to B2O3 increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

Preparation of Integrated Passive Microwave Devices Through Inkjet Printing

Barium strontium titanate (BST) is a promising material for passive tunable microwave devices such as phase shifters or tunable matching networks. This publication covers the preparation of BST thick-films for microwave applications through inkjet printing. Two barium strontium titanate (BST) inks were prepared, printed on alumina substrates and sintered at different temperatures. The first ink was prepared with pure BST and sintered between 1100°C and 1200°C. The second ink was prepared with a BST–ZnO–B2O3 composition and was suitable to reduce the sintering temperature down to 800°C. The microstructure of the thick-films reveals the evolution of grain growth with increasing sintering temperature in the thick-films. Furthermore, a reaction with the substrate was observed for both inks at high sintering temperatures. The microwave characterization of the thick-films shows that for the permittivity and the tunability of the films, the effect of grain growth and reaction with the substrate compete against each other. Hence, the optimal microwave properties were achieved at a transition temperature, where first additional phases could already be observed. Even though, the properties are poorer for lower sintering temperatures, the investigations show that the preparation of silver- or gold-based metal–insulator–metal (MIM) structures through inkjet printing is possible with this composition. This allows various new design concepts for partly or fully inkjet printed passive microwave devices. Furthermore, it gives the opportunity for a future integration of passive tunable microwave devices in a low temperature co-fired ceramic (LTCC) fabrication process.

Ophthalmologic glass with enhanced refractive index

Glasses with refractive index 1.60 – 1.65, density 2.80 – 3.08 g/cm3 and dispersion coefficient ≥ 45 have been developed on the basis of the system Na2O(K2O)–MgO–CaO–BaO–ZnO–B2O3–SiO2. These glasses are recommended for use in ophthalmologic lenses.

Synthesis of nanosized glass powders using non-transferred dc thermal plasma process

The fabrication of nanosized Bi2O3–ZnO–B2O3 based glass powder using a non-transferred direct current plasma process was examined. This paper discusses the amorphous and crystalline nature of glass systems that contain bismuth oxide after plasma treatment. The addition of a reactive gas (O2) enhanced the amorphous nature of the glass powder by preventing the thermal dissociation of Bi2O3 into nanosized bismuth particles. Transmission electron microscopy revealed the spherical shape of the powders with a size of 10–60 nm. A minor change of <1 mol.-% in the resulting powder composition was confirmed by inductively coupled plasma–optical emission spectrometry measurements. The nanosized glass powders began to shrink at 340°C, which is 50°C lower than the temperature at which micrometre sized glass powders begin shrinking. Fundamental information for the size reduction of the multicomponent glass system using dc thermal plasma technique as well as thermal behaviour was provided.

A new route to improve microwave dielectric properties of low-temperature sintered Li2TiO3-based ceramics

Low-temperature sintered Li2TiO3-based ceramics for low temperature co-fired ceramic resonators were synthesized by a solid state reaction method. Their microwave dielectric properties were further improved by CeO2 addition. When the amount of CeO2 increased, the relative permittivity (er) of the samples increased a little and then decreased. The quality factor (Q × f) of the samples was improved obviously for a higher standard reduction potential of cerium than that of titanium. The temperature coefficient of resonant frequency (τf) of the samples decreased with the increase of CeO2 addition. CeO2 mainly existed as a secondary phase and it facilitated the sintering of the Li2TiO3-based ceramics. Typical microwave dielectric properties of er = 22.97, Q × f = 34,881 GHz, and τf = 33.12 ppm/°C were obtained for Li2TiO3 + 2 wt% ZnO–B2O3 frit + 0.9 wt% CeO2 ceramics sintered at 920 °C for 4 h. The addition of oxidizers was proved a promising route to improve the microwave dielectric properties of titanate ceramics sintered at low temperatures.

Effects of ZnO–B2O3 Addition on the Microstructure and Microwave Properties of Low‐Temperature Sintered Barium Strontium Titanate (BST) Thick Films

BST–ZnO–B2O3–composite thick films have been investigated regarding their suitability as low‐temperature sintered tunable microwave dielectrics. The investigations showed that already a small amount of ZnO–B2O3 additive can remarkably reduce the sintering temperature down to 900°C. Microstructural investigations of the thick films revealed the formation of an amorphous intergranular phase and a clustering of particles for high additive amounts. The microwave characterization showed a reduction in relative permittivity, dielectric loss, and tunability of the thick films with increasing additive content. These results demonstrate the potential to tailor the material abilities by varying the additive content.

Microstructures, phases, and properties of low melting BaO–B2O3–ZnO glass films prepared by pulsed laser deposition

With the motivation to employ BaO–B2O3–ZnO for high performance capacitors by using viscous flow/liquid phase sintering, the microstructures, phases, and dielectric properties of BaO–B2O3–ZnO films prepared by pulsed laser deposition were examined as a function of heat-treatment. The glass transition temperature (Tg) and crystallization temperature of the films are ~536°C and 640°C, respectively. The phases in the films are quite complicated after heat-treated above 700°C until 900°C where the film is dominated by a single phase. Zn concentration is reduced after heat-treatment at high temperature due to segregation and evaporation. The dielectric constant of the film decreases with the increasing heat-treatment temperature, probably due to Zn reduction, Si diffusion, and crystallization of the film. Experimental data shows that ~700°C is the optimal temperature to use the low melting glass BaO–B2O3–ZnO to make high performance capacitors by viscous flow/liquid phase sintering.

Effects of alkaline-earth fluorides and OH− on spectroscopic properties of Yb3+ doped TeO2–ZnO–B2O3 based glasses

New kinds of Yb2O3-doped boro-tellurite (TeO2–ZnO–B2O3) based glasses were prepared by introducing alkaline-earth fluorides (MgF2, CaF2, SrF2, and BaF2). Their structural and spectroscopic properties were investigated by Raman and absorption spectra measurements. Dehydration ability of alkaline-earth fluorides was studied. The OH can have an obvious effect on fluorescence lifetime of Yb3+, when OH concentration is higher than NOH=4.66×1019cm−3. For TeO2–ZnO–B2O3–BaF2 glass system, the peak values of integrated absorption and emission cross-sections achieve 7.44×104pm3 and 1.416pm2, respectively. It indicates that the Yb3+-doped boro-tellurite glasses containing alkaline-earth fluorides are potential materials for waveguide laser, and optical amplifier.

Effect of borosilicate glasses on the microwave dielectric properties of ZnO–Nb2O5–Ta2O5 system

(1 − y)[0.5ZnNb2O6–0.5Zn3Nb2O8]–yZnTa2O6 with y = 0.91 (ZNT) ceramic have been prepared by conventional solid state ceramic route. The effect of glass additives on the microstructure, densification, and microwave dielectric properties of the ZNT ceramic for low temperature co-fired ceramic applications was investigated. Different weight percentages of quenched glass such as ZnO–B2O3–SiO2, BaO–B2O3–SiO2, LiO–B2O3–SiO2 and MgO–B2O3–SiO2 were added to ZNT powder. The crystal structure of the ceramic–glass composites was studied by X-ray diffraction and microstructure by scanning electron microscopy. The microwave dielectric properties such as relative permittivity (er), quality factor (Quxf) and co-efficient of temperature variation of resonant frequency (τf) of the ceramics have been measured in the frequency range 4–6 GHz. The 5 wt% ZnO–B2O3–SiO2 added ZNT ceramic sintered at 900 °C showed: er = 28.1, Quxf = 32820 GHz (at 4.92 GHz), and τf = −7.7 ppm/oC respectively.

The effect of composition on Li2(Mg0.3Zn0.7)Ti3O8–xTiO2 microwave dielectric ceramics for low temperature co-fired ceramics technology application

The effect of composition of Li2(Mg0.3Zn0.7)Ti3O8–xTiO2 (−0.36≤x≤0.36, for short LMZT) on sinterability, crystalline phase, microstructure and microwave dielectric properties of the ZnO–B2O3–SiO2 (for short ZBS) glass doped samples was systematically investigated. It shows that as x is over zero, rutile phase was detected and the crystalline grain size of LMZT ceramics decrease abruptly. It was also found that the bulk density and the quality factor (Q×f) gradually decreased, dielectric constant (εr) increased, the temperature coefficient of resonant frequency (τf) shifted to positive value with the increase of x value. When x=0.12, LMZT ceramics with 3wt% ZBS sintered at 900°C for 3h show excellent dielectric properties: εr=25.1, Q×f=19,620GHz, τf=−2.3ppm/°C. It is compatible with Ag electrodes, which makes it a promising ceramic for low temperature co-fired ceramics technology application.

Phase evolution and electrical properties of copper-electroded BaTi4O9 materials with BaO–ZnO–B2O3–SiO2 glass system in reducing atmosphere

BaTi4O9 (BT4) microwave dielectric ceramics using a copper electrode and containing 10wt% BaO–ZnO–B2O3–SiO2 (BZBS) glass frit were sintered under reducing atmosphere at 950°C and were investigated on the phase evolutions, microstructures and dielectric properties of BT4 with various BaO/SiO2 and ZnO/SiO2 ratios of BZBS glasses. Experimental results show that the BaO/SiO2 ratio contributes to wettability of glass with BaTi4O9 ceramics, and ZnO/SiO2 ratio determines the densification of BaTi4O9 ceramics. The different Ba–Ti–O and Ba–Cu–O phases with various Ba/Ti and Ba/Cu ratios can be attributed to the contents of BaO in glass. Ba4Ti13O30 and Ba2Cu3O5+X may form when BaO contents are too high, and inducing copper diffusion due to the reactions of BaO and Cu, accompanying with degrading of the dielectric characteristics. If the ZnO contents of BZBS glasses were raised, a little bit of ZnSiO3 and Ba2Cu3O5+X phases appear without Cu diffusion due to non-reaction of ZnO and CuO. The high ZnO/SiO2 ratio of glass reveals the lower softening point, indicating that the high ZnO glass could enhance the density and therefore increase the dielectric constant and quality factor.