Structural and up-conversion luminescence properties in Tm (3+)/Yb3+-codoped heavy metal oxide-halide glasses

Tm3+/Yb3+-codoped heavy metal oxide-halide glasses have been synthesized by conventional melting and quenching method. Structural properties were obtained based on the Raman spectra, indicating that halide ion has an important influence on the phonon density and maximum phonon energy of host glasses. Intense blue and weak red emissions centered at 477 and 650 nm, corresponding to the transitions (1)G(4) -> H-3(6) and (1)G(4) -> H-3(4), respectively, were observed at room temperature. The possible up-conversion mechanisms are discussed and estimated. With increasing halide content, the up-conversion luminescence intensity and blue luminescence lifetimes of Tm3+ ion increase notably. Our results show that with the substitution of halide ion for oxygen ion, the decrease of phonon density and maximum phonon energy of host glasses both contribute to the enhanced up-conversion emissions. (c) 2005 Elsevier B.V. All rights reserved.

Phi 140 mm sapphire crystal growth by temperature gradient techniques and its color centers

Sapphire crystals, 140 mm in diameter and 90 turn in height, have been grown by temperature gradient techniques (TGT). The growth direction of the boule was fixed by means of Lane X-ray diffraction. A prominent 204 nm absorption band in TGT-Al2O3. which does not appear in single crystals grown by Czochralski method has been studied. Analysis further substantiates the F-center model of this band. Two relatively weaker bands absorbing at 232 nm and 254 nm were ascribed to F+ centers. F-type centers concentration was determined using Smakula's equation. (c) 2005 Elsevier B.V. All rights reserved.

白宝石晶体的高温强度及强化技术研究进展

白宝石高温强度的降低主要是由于c轴方向受到压应力时产生r面双晶所引起的。高温强度的下降导致其抗热震性能降低，从而限制了白宝石晶体作为红外窗口和头罩材料的应用。白宝石晶体的强化主要以消除双晶核以及控制双晶的扩展来实现。本文分析了影响白宝石强度的主要因素，在此基础上对目前白宝石晶体强化的方法进行了总结和分析。