{"title":"1D to 2D Growth of NaF Crystals in Photothermo-Refractive Glasses","authors":"Zhixiang Li, Qiuping Ren, Yuanxing Chang, Dashuang Ding, Leilei Ma, Yinsheng Xu, Shaoqian Zhang, Xianghua Zhang","doi":"10.1021/acs.cgd.4c00882","DOIUrl":null,"url":null,"abstract":"The precipitation of NaF crystals with a low refractive index only in the UV exposure region is essential to obtain high refractive index change in photothermo-refractive (PTR) glass for producing high-performance volume Bragg gratings (VBGs). However, the precision control of the growth of NaF crystals in the UV exposure region of PTR glass remains challenging. In this work, the effect of Al<sub>2</sub>O<sub>3</sub> on the crystallization behavior of NaF crystals in PTR glass was investigated using the nonisothermal crystallization kinetic method. After photothermal-induced nucleation, the crystallization activation energy (<i>E</i><sub>a</sub>) of PTR glass decreased first and then increased with the rise in the Al<sub>2</sub>O<sub>3</sub> content. The appropriate amount of Al<sub>2</sub>O<sub>3</sub> (4 mol %) is helpful for reducing the <i>E</i><sub>a</sub> and promoting the formation of NaF crystals. The crystal growth index (<i>n</i>) and crystal growth dimension (<i>m</i>) suggest that the crystallization behavior of NaF crystals was photothermally induced nucleation and crystallization of 1D growth. The increasing trend of the <i>m</i> values indicates that the crystals tend to transit from 1D to 2D growth with the increase in Al<sub>2</sub>O<sub>3</sub> content. When Al<sub>2</sub>O<sub>3</sub> is 6 mol %, <i>n</i> equals <i>m</i> + 1, which implies the NaF crystals crystallize spontaneously rather than growing on the Ag nuclei. The crystals observed using scanning electron microscopy images showed that irregular precursors appeared first and then grew into needle-like crystals. When the NaF crystals grew sufficiently long, they transformed into lamellar crystals. This work elucidates the crystallization process of NaF crystals in PTR glass and provides guidance for the production of high-performance VBGs.","PeriodicalId":34,"journal":{"name":"Crystal Growth & Design","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Crystal Growth & Design","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.1021/acs.cgd.4c00882","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The precipitation of NaF crystals with a low refractive index only in the UV exposure region is essential to obtain high refractive index change in photothermo-refractive (PTR) glass for producing high-performance volume Bragg gratings (VBGs). However, the precision control of the growth of NaF crystals in the UV exposure region of PTR glass remains challenging. In this work, the effect of Al2O3 on the crystallization behavior of NaF crystals in PTR glass was investigated using the nonisothermal crystallization kinetic method. After photothermal-induced nucleation, the crystallization activation energy (Ea) of PTR glass decreased first and then increased with the rise in the Al2O3 content. The appropriate amount of Al2O3 (4 mol %) is helpful for reducing the Ea and promoting the formation of NaF crystals. The crystal growth index (n) and crystal growth dimension (m) suggest that the crystallization behavior of NaF crystals was photothermally induced nucleation and crystallization of 1D growth. The increasing trend of the m values indicates that the crystals tend to transit from 1D to 2D growth with the increase in Al2O3 content. When Al2O3 is 6 mol %, n equals m + 1, which implies the NaF crystals crystallize spontaneously rather than growing on the Ag nuclei. The crystals observed using scanning electron microscopy images showed that irregular precursors appeared first and then grew into needle-like crystals. When the NaF crystals grew sufficiently long, they transformed into lamellar crystals. This work elucidates the crystallization process of NaF crystals in PTR glass and provides guidance for the production of high-performance VBGs.
期刊介绍:
The aim of Crystal Growth & Design is to stimulate crossfertilization of knowledge among scientists and engineers working in the fields of crystal growth, crystal engineering, and the industrial application of crystalline materials.
Crystal Growth & Design publishes theoretical and experimental studies of the physical, chemical, and biological phenomena and processes related to the design, growth, and application of crystalline materials. Synergistic approaches originating from different disciplines and technologies and integrating the fields of crystal growth, crystal engineering, intermolecular interactions, and industrial application are encouraged.