Prasad N S, Varma K B
Materials Research Centre, Indian Institute of Science, Bangalore 560 012, India.
J Nanosci Nanotechnol. 2001 Dec;1(4):425-32. doi: 10.1166/jnn.2001.052.
Transparent glass composites in the system (100 - x) Li2B4O7 - x SrBi2Nb2O9 (where x = 5, 10, 15, 20, 25, and 30, in molar ratio) were fabricated by conventional melt-quenching technique. The amorphous nature of the as-quenched glass composites was confirmed via X-ray powder diffraction (XRD) studies. Differential thermal analyses (DTA) established the glassy nature of the as-quenched samples. Glass nanocomposites (GNC's) with high-optical transparency were obtained by controlled heat-treatment of the glass composites at 750 K/6 h. Perovskite SrBi2Nb2O9 (SBN) phase formation through an intermediate fluorite phase was confirmed by XRD and transmission electron microscopy (TEM). The dielectric constant (epsilon r) in the frequency range from 100 Hz to 40 MHz at room temperature increases whereas dielectric loss (D) decreases with increase in SBN content in Li2B4O7 glass matrix. Impedance spectroscopy employed to rationalize the electrical behavior of the as-quenched glasses and glass nanocomposites suggests the coexistence of electronic and ionic conduction in these materials. The optical transmission and band-gap energy of these composites were found to be crystallite size dependent.
采用传统的熔体淬火技术制备了体系为(100 - x)Li2B4O7 - x SrBi2Nb2O9（其中x = 5、10、15、20、25和30，摩尔比）的透明玻璃复合材料。通过X射线粉末衍射（XRD）研究证实了淬火态玻璃复合材料的非晶性质。差示热分析（DTA）确定了淬火态样品的玻璃性质。通过在750 K下对玻璃复合材料进行6小时的控制热处理，获得了具有高光学透明度的玻璃纳米复合材料（GNC）。通过XRD和透射电子显微镜（TEM）证实了通过中间萤石相形成钙钛矿SrBi2Nb2O9（SBN）相。室温下，在100 Hz至40 MHz频率范围内，随着Li2B4O7玻璃基体中SBN含量的增加，介电常数(εr)增大，而介电损耗(D)减小。用于合理化淬火态玻璃和玻璃纳米复合材料电学行为的阻抗谱表明这些材料中存在电子传导和离子传导。发现这些复合材料的光传输和带隙能量与微晶尺寸有关。
