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The aim of this study is to investigate the impact of the Kovar glass content on the mechanical and electrical properties of Si3N4–Kovar composites sintering at air atmosphere. To achieve this, Si3N4–Kovar composites were prepared using molding technology with the Kovar glass powder ranging from 20 to 70 wt%. The phase composition, morphology, bulk density, apparent porosity, flexural strength at room temperature, dielectric constant, and dielectric loss of the composites were all examined in relation to changing the Kovar glass content. During the sintering process, the α‐quartz on the surface of Si3N4 particles acted as the crystal nucleus, inducing the crystallization of the glass at the wetting position that the Kovar glass and the surface of the Si3N4 particles. A small amount of the β‐quartz phase was crystallized at 750–850°C, followed by a large amount of the β‐quartz phase crystallizing above 900°C. Additionally, some β‐quartz phase transformed into the metastable β‐cristobalite phase that could exist below 1470°C. During the cooling process, the β‐cristobalite phase transformed into a low‐temperature α‐cristobalite phase, while the β‐quartz phase transformed into a low‐temperature α‐quartz phase. The results indicate that the Si3N4–Kovar glass composite with 60 wt% the Kovar glass content sintered at 900°C exhibits higher density (1.88 g/cm3), lower porosity (25.4%), higher flexural strength (55.34 MPa), lower dielectric constant (3.46), and lower dielectric loss (4.26 × 10−3). [ABSTRACT FROM AUTHOR]

The efficient 810 nm laser energy conversion of glass frit had been proven to be the key to the long‐term hermetic encapsulation of Organic Light Emitting Display (OLED). A direct laser energy conversion laser‐assisted Bi2O3‐B2O3‐ZnO‐Nd2O3 sealing glass material without extra laser absorbent such as carbon black, was designed and systematically investigated. The addition of Nd2O3, as glass modifiers with higher cationic field strength, could be conducive to enhancing the polymerization of glass network structure, manifesting that the glass‐transition temperature Tg, onset‐crystallization temperature Tc and thermal stability ΔT (ΔT = Tc‐Tg) increased, while thermal expansion coefficient CTE dropped to 9.72×10−6/°C and advantageously matched with the glass substrate (8±1×10−6/°C). More importantly, the absorption rate of BBZ‐Nd glass was more than 50 % between 800∼810 nm owing to the 4f‐4f electron transition of Nd3+ ions, and yet the reflectivity and transmittance of the wavelength at 800–810 nm were lower. As optimal compositions, the addition of 3.0 wt% Nd2O3 in Bi2O3‐B2O3‐ZnO‐Nd2O3 glass frit with higher absorption coefficients (80 %) led to instantaneous bonding encapsulation between glass substrates without interfacial cracks or pores with the 808 nm wavelength of the laser at 20 W and 2.4 mm/s. [ABSTRACT FROM AUTHOR]

The development of mid‐infrared (MIR) broadband tunable lasers urgently needs high performance laser gain materials. Transition metal (TM) ions doped glass ceramics are considered to be efficient MIR broadband laser gain media. However, it is difficult to achieve gain because of the large scattering loss and low luminescence efficiency. In this paper, GeS2–Sb2S3–CsI–PbI2 chalcohalide glass ceramics containing CsPbI3 perovskite nanocrystals are fabricated by the melt‐quenching method and subsequent heating treatment. The crystallization behavior of CsPbI3 nanophase and MIR luminescence properties of Ni2+ dopant are systematically investigated. Evidently, spherical CsPbI3 perovskite nanocrystals are precipitated and uniformly distributed in the glassy matrix, which can reduce the light scattering and make the chalcohalide glass ceramics have a high transparency. Moreover, an ultra‐broadband MIR emission in the range of 2.5–5.5 μm is observed for the first time, to our best knowledge, from Ni2+‐doped chalcohalide glass ceramics containing CsPbI3 perovskite nanocrystals. The newly developed Ni2+‐doped chalcohaldie glass ceramics could be promising gain media for MIR broadband tunable lasers. [ABSTRACT FROM AUTHOR]

Abstract: Four MgO‐Ta2O5 ceramics with the MgO/Ta2O5 mole ratio x = 1, 2, 3, and 4 were prepared by traditional solid‐state reaction method, and the influence of x on the phase composition, microstructure, and dielectric properties (the dielectric constant εr, the temperature coefficient of resonant frequency τf and the quality factor Qf) of the materials was investigated using XRD, SEM, etc. The results indicated that the ceramics were composed of two crystalline phases MgTa2O6 and Mg4Ta2O9 in the composition range studied, and that the dielectric properties ln ε, 1/Qf, and τf changed proportionally to the fraction of main crystal phases, which meet perfectly with the mixing model proposed in this study. It is obvious that the proportion of the two crystal phases could be precisely controlled by x, and thereby, the dielectric properties can be conveniently and precisely tailored. Our research provided a new microwave dielectric ceramic with the composition of 2MgO‐Ta2O5, which has an ultrahigh Qf value (211 000 GHz), low dielectric constant εr (19.9), and near zero temperature coefficient of resonant frequency τf (8 ppm/°C). [ABSTRACT FROM AUTHOR]

The (1− x)Mg2Al4Si5O18- xTiO2 |(1− x) MAS- xT| (0 ≤ x ≤ 0.35) cordierite ceramics are fabricated by solid-state reaction method for obtaining near-zero temperature coefficient of resonant frequency (τf). The XRD and SEM results show that (1− x) MAS- xT (0 ≤ x ≤ 0.10) ceramics exhibit single cordierite solid solution, whereas as 0.15 ≤ x ≤ 0.35, present composite phases of Mg2Al4Si5O18 solution and TiO2. Rietveld refinements of XRD data suggest that the [(Si4Al2)O18] hexagonal shape in cordierite structure happens to alternate change from nonsymmetrical hexagonal rings to almost centrosymmetrical equilateral rings as x increases to 0.10 comparing to that of x = 0. As Ti4+ ions squeeze into the [(Si4Al2)O18] rings structure, the orientation and shapes of the rings begin to rotate and expand from initial state of [1-20] ( x = 0) to near [210] direction ( x = 0.10), and then continue to expand toward close to [110] direction ( x = 0.25). Due to centrosymmetry adjustment of [(Si4Al2)O18] hexagonal rings and of other microstructure factors improvement, the (1− x) MAS- xT ( x = 0.10) cordierite solution achieves optimum quality factor Qf: εr = 6.3, Qf = 55 400 GHz (17.6 GHz), τf = −21 ppm/°C. The (1− x) MAS- xT ( x = 0.25) composites obtain a near-zero temperature coefficient of resonance frequency: εr = 6.8, Qf = 37 800 GHz (18.4 GHz), τf = −0.2 ppm/°C. [ABSTRACT FROM AUTHOR]

Mg1/3A11/3A21/3Ta2O6 ceramics (where A1 and A2 represent Co, Ni, or Zn) were prepared using the solid‐phase reaction route. The results of X‐ray diffraction and Raman tests showed that (Co1/2Ni1/2)2+, (Co1/ 2Zn1/2)2+, and (Ni1/2Zn1/2)2+ ions replaced Mg2+ ions in the lattice of MgTa2O6, resulting in the formation of a pure tri‐rutile structure. All three complex ions could significantly reduce the sintering temperature of the ceramics (by 150°C–200°C) and could broaden the sintering window. The large deviation (48.8%–69.2%) between the porosity corrected relative permittivity εr‐corr. and the theoretical relative permittivity εr‐theo. might be due to the overestimation of the ionic polarizability of Ta5+ by Shannon. (Co1/2Ni1/2)2+ has the most significant effect of increasing the bond energy of ceramic A–O bonds, reducing the τf value from 51 to 36 ppm/°C. In addition, the mechanisms affecting their dielectric properties are discussed based on bond ionicity (fi), full width at half maximum (FWHM) of Raman peak, and bond energy (E). Mg1/3Co1/3Ni1/3Ta2O6 ceramic sintered at 1350°C have the most excellent microwave dielectric properties: εr = 26.8, Q × f = 86,000 GHz, and τf = 36 ppm/°C. [ABSTRACT FROM AUTHOR]

The increased coefficient of thermal expansion (CTE) mismatch and mechanical performance degradation of glass‐based sealant‐induced thermal stress are critical issues for long‐term application of solid oxide fuel cell (SOFC). In this work, the double effect of MgO particle on dispersion strengthening, inhibition low‐CTE phase transformation, thermal stress, and leakage rate in BaO‒CaO‒Al2O3‒B2O3‒SiO2 (BCABS) glass‐ceramic were investigated and analyzed. The low‐CTE mono‐BaAl2Si2O8 phase was suppressed by the MgO particle reacting with BCABS glass‐ceramic. Consequently, the CTE for BCABS glass‐ceramic without MgO decreases from 11.47 at 1 h to 10.18 ×10−6/°C at 1000 h and reduction rate is higher than 10%, bring about the thermal stress of sealant itself and interface had tripled (200 MPa) and leakage rate was high than 0.06 sccm/cm after 250 h. However, the CTE of 20 wt% MgO‐reinforced BCABS glass‐ceramic sealant only declined about 4.0% for 1000 h, resulting in slow increase or even decrease in the thermal stress (low than 60 MPa) and maintaining stable leakage rate below 0.04 sccm/cm for 1000 h with three thermal cycles. This study was useful for identifying optimal CTE matching and elastic modulus of glass‐based sealant for efficient and stable long‐term operation of SOFC. [ABSTRACT FROM AUTHOR]