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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Effect of cooling on the optical properties and crystallization of UV-exposed photo-thermo-refractive glass
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Effect of cooling on the optical properties and crystallization of UV-exposed photo-thermo-refractive glass

机译：冷却对曝光于紫外线的光热折射玻璃的光学性能和结晶的影响

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摘要

Photo-thermo-refractive (PTR) glass is a multi-component silicate glass that undergoes a refractive index change after UV-exposure and thermal treatment. This photo-thermo-refractivity is due to the precipitation of sodium fluoride nano-crystals; thus the glass remains highly transparent in the visible and near-IR regions. Up to now, most studies focused on the influence of temperature and duration of thermal treatment on the PTR glass properties, but no attention was given to the cooling step after thermal treatment. In this paper, the influence of cooling on crystallization and resulting optical properties of UV-exposed PTR glass is studied. We show that cooling between the nucleation and growth treatments is a mandatory step to achieve the full benefits of the first heat-treatment, i.e., a large number of small crystals. We also show that the main part of the refractive index change occurs on the cooling path after pre-nucleation. Non-isothermal DSC study associated with in situ pre-nucleation treatment shows that pre-nucleation enhances crystallization only if the temperature is decreased below T-g before the second (development) treatment. Using high temperature photometric measurements of the absorption spectra of UV-exposed PTR glasses, we tentatively associate that effect with the presence of liquid drops of a silver containing phase during regular pre-nucleation treatment. This fact explains the necessity to cool such drops below their melting point to obtain nucleation centers for efficient precipitation of NaF nano-crystals.
机译：光热折射（PTR）玻璃是一种多组分硅酸盐玻璃，在经过紫外线曝光和热处理后会发生折射率变化。这种光热反射性是由于氟化钠纳米晶体的沉淀所致。因此，玻璃在可见光和近红外区域保持高度透明。迄今为止，大多数研究集中在温度和热处理持续时间对PTR玻璃性能的影响上，但是对热处理后的冷却步骤没有给予任何关注。在本文中，研究了冷却对暴露于紫外线的PTR玻璃的结晶及其光学性能的影响。我们表明，成核和生长处理之间的冷却是获得第一热处理的充分好处的强制性步骤，即大量小晶体。我们还表明，折射率变化的主要部分发生在预成核后的冷却路径上。与原位预成核处理相关的非等温DSC研究表明，只有在第二次（显影）处理之前将温度降低到T-g以下，预成核才能增强结晶。通过对暴露于紫外线的PTR玻璃的吸收光谱进行高温光度测量，我们将这种影响与常规预成核处理期间含银相液滴的存在联系起来。这一事实解释了将此类液滴冷却至其熔点以下以获得成核中心以有效沉淀NaF纳米晶体的必要性。

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