Borate glass (80B(2)O(3)-20Bi(2)O(3) in mol.%), which had a coefficient of thermal expansion (CTE) that was exceptionally compatible with that of sapphire, was designed and used as a braze to join sapphire. Prior to joining, various thermodynamic properties of the glass were investigated. Brazing was conducted at 600-750 degrees C, and the influence of the brazing parameters on the microstructural evolution and mechanical properties of the joints were investigated. The results showed that two crystalline phases, Bi6B10O24 and Bi48Al2O75, were formed in the joint due to crystallization within the glass, which could strengthen the joint. The maximum shear strength, 55.5 MPa, was achieved for the joint that was brazed at 725 degrees C for 20 min. The finite element method (FEM) was utilized to simulate the shear stress during cooling. Analysis of the residual stress in the FEM simulation showed that the shear stress was mainly concentrated near the sapphire/glass interface.

Borate based glass, 25Bi2O3–75B2O3 (mol.%), was employed as a braze to join sapphire in an atmospheric environment. The crystallization behaviour as well as the crystallization kinetics of the glass during the heating process were investigated in a variety of ways. Wetting tests were conducted to research the wetting and spreading performances of the glass on the surface of sapphire prior to joining. Furthermore, sapphire joints were reliably obtained under various joining parameters. The dependence of the microstructural evolution and mechanical performance of sapphire joints on temperature and dwell time were also explored. The research results indicate that 25Bi2O3–75B2O3 glass possesses outstanding glass-forming ability and excellent wettability on the surface of sapphire. Bi6B10O24 crystalline phases were produced in the seam. The width of the joint as well as the quantity of Bi6B10O24 crystals increased at first and then decreased with the extension of dwell time. Simultaneously, the shear strength of the joints had a tendency to improve gradually and then diminish with the rise in brazing temperature. The maximum strength of the joints (49.3 MPa) was obtained by brazing at 700 °C for 20 min.

Alumina ceramics and copper were vacuum brazed using a bismuth-borate-zinc glass at temperatures between 660 and 720 degrees C for 20 min. The interfacial phases were characterized and the influence of brazing temperatures on microstructure of the joints were investigated. Shear tests of brazed joints under different conditions were also performed, and the joint fracture was observed and analyzed to determine the influence of brazing temperatures on the joint mechanical properties. Al2O3 ceramic/Al2O3 + glass phase/ZnAl2O4 + glass phase/(Ni, Cu)O/Ni(s.s) + BiNi/copper was identified as the main structure of the Al2O3 joints brazed with the glass. As the brazing temperature increased, the (Ni, Cu)O oxide layer in the joint was observed to thicken and extend to both sides gradually. The amount of BiNi formed in the Ni coating layer increased, and the scattered znAl(2)O(4) particles gradually grew. When the brazing temperature reached 700 degrees C, ZnAl2O4 particles agglomerated on the alumina ceramic side, and glass permeated into the alumina base material, The shear strength of the joint first increased and then decreased with the increase of brazing temperature. The shear strength reached the maximum value of 21.1 MPa when brazed at 680 degrees C.

Polycrystalline alumina ceramics were air-brazed using bismuth glass with a chemical composition of 50Bi(2)O(3)-40B(2)O(3)-10ZnO (mol.%) at a relatively low temperature. ZnAl2O4 particles were formed insitu in the joints and the particles grew rapidly with an increase in joining temperature and holding time increasing. In addition, penetration of the alumina substrate by the glass became increasingly serious at higher temperatures and holding durations. The mechanical properties of the joints were investigated and the maximum shear strength was determined to be 50 MPa when brazed at 650 degrees C for 0 min.

HgIn2Te4 (Mercury indium telluride, MIT) is a promising mid-infrared CO2 laser candidate material. Through combining the calculation results of structural relaxation, Bader charge, electronic localization function, formation energy, and density of states, we systematically explored the stability and doping efficiency of gold (Au) in MIT. The results show that the Au-Te bond has a similar polar covalent characteristic as Hg-Te bond, which indicates the relative stability of Au dopant in MIT. In addition, two defect states were formed through the hybridization between the Au impurity and its nearest neighboring Te atoms in the substitutional doping systems of AuHg and AuIn. We found that the acceptor transition levels in AuHg and AuIn are 0.095 eV and 0.265 eV above the valance band maximum, respectively, whereas the donor transition level in the substitutional doping system of AuTe and interstitial system of AuI are 0.894 eV and 0.322 eV below the conduction band minimum, respectively. Meanwhile, in the Hg-rich condition, the Fermi level would be pinned about 0.511 eV above the valence band maximum due to the self-compensation effect; however, this effect will be efficiently reduced in the Te-rich condition.