The thermal stability and spectroscopic properties of Er3+-doped Na2O-GeO2-PbO glasses were investigated experimentally. The thermal analysis results show that the thermal stability of the investigated glasses is improved with replacing GeO2 by PbO. Subsequently, Judd-Ofelt (J-O) approach was applied to the room temperature absorption of Er3+ (4f 11) transitions to determine J-O intensity parameters. The reduced values of Ω2 with the substitution of PbO for GeO2 indicate the decrease of covalency of Er O bonding. The stimulated emission cross section of the 4-13-2→4I15-2 transition increases as a consequence of the increase of refractive index of glass hosts and the narrowing of fluorescence bandwidth with the increase of PbO. The abnormal large emission cross section and large bandwidth in the Na2O-0.8GeO2-0.1PbO glass arises from the change of germanium coordination with oxygen.

Yb3+-Er3+ co-doped Na2O-GeO2-PbO glass suitable for developing optical fiber lasers and amplifiers has been fabricated. The energy transfer efficiency from Yb3+ to Er3+ was investigated in the glasses with different Yb3+-Er3+ concentration ratios and the maximum energy transfer efficiency was found to be 67% at the Yb3+-Er3+ concentration ratio of 5:1. Subsequently, the studies of upconversion emissions in the visible range were performed. An intense green together with a relatively weak red emission was observed under the excitation of 976nm diode laser. The quadratic dependence of the green emission on excitation power indicates that a two-photon absorption process occurs under a 976nm excitation. However, for the red emission the slope of log-log plot of integrated intensity versus pump power declines with increasing Yb3+ ions content, indicating it is not resulted from a biphotonic process.

In this article, we present a study of a new glass system: lead-germanium-tellurite glasses in the form of 0.05K2O-0.1ZnO-0.1BaO-0.2PbO-xGeO2-(0.55-x) TeO2 with x 0.1, 0.2, 0.3, 0.4, 0.5, and 0.55. Differential temperature analysis of this glass system shows that increasing GeO2 content raises the glass transition temperature (Tg) and suppresses the crystallization tendency in a large temperature range from Tg to the glass melting temperature. The maximum vibrational frequency is intermediate between germanate and fluoride glasses, in the range of 750cm-1 to 820cm-1. Subsequently, Optical absorption, photoluminescence, and upconversion fluorescence were measured for Yb3+, Er3+ co-doped lead-tellurium-germanate glasses. It was found that the full width at half-maximum of the luorescence spectrum at 1534nm decreases and the measured radiative lifetime increases with the replacement of TeO2 by GeO2. Excitation at 976nm into the glass system leads to an intense green emission and a relatively weak red emission. With the addition of GeO2, the increase of red fluorescence and the decrease of green emission in intensity are due to the increase of nonradiative transition rates between the 4S3-2 and 4F9-2 states of Er3+ions. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption process occurs in this glass system excited at 976nm.

With the addition of the sintering additives Ni and Cu, highly dense Mo-Ti alloys with various Mo:Ti ratios were obtained byhot-pressing method. Under the same conditions a Mo-Ti green body with continuously graded com position, formed by the particle settling method, was sintered. The longitudinal and transverse ultrasonic velocities of Mo-Ti alloys were tested in order to calculate the residual stresses that develop during cooling of the Mo-Ti functionally graded material (FGM). By using an axisymmetric finite element method, the fabricated thermal stress in a disk-shaped Mo-Ti FGM was calculated. The results show that the residual stress continuously changes with the smooth change of graded composition and the maximum value of residual tensile stress is far lower than that of the bending strength of Mo-Ti alloys.