{"id":2688,"date":"2026-04-20T02:31:09","date_gmt":"2026-04-20T02:31:09","guid":{"rendered":"https:\/\/www.fuyao-quartz.com\/?p=2688"},"modified":"2026-04-20T02:31:54","modified_gmt":"2026-04-20T02:31:54","slug":"manufacturing-technologies-of-fused-silica","status":"publish","type":"post","link":"https:\/\/www.fuyao-quartz.com\/fi\/manufacturing-technologies-of-fused-silica\/","title":{"rendered":"Manufacturing Technologies of Fused Silica: From Natural Quartz Melting to Advanced Synthetic Processes"},"content":{"rendered":"<h2 class=\"wp-block-heading\">1. Johdanto<\/h2>\n\n\n\n<p>Fused silica (SiO\u2082) is a critical material widely used in optics, semiconductors, and high-temperature engineering due to its exceptional purity, thermal stability, and optical performance. Its manufacturing technologies can be broadly classified into two major categories: natural fused silica and <a href=\"https:\/\/www.fuyao-quartz.com\/fi\/products\/\">synthetic fused silica<\/a>.<\/p>\n\n\n\n<p>The fundamental distinction lies in raw material sources, which subsequently determines the processing routes, impurity profiles, and final material performance.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"800\" src=\"https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components.jpg\" alt=\"sulatetut kvartsi-ikkunat - eritt\u00e4in puhtaat optiset siirtokomponentit\" class=\"wp-image-2341\" srcset=\"https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components.jpg 800w, https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components-300x300.jpg 300w, https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components-150x150.jpg 150w, https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components-768x768.jpg 768w, https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components-600x600.jpg 600w, https:\/\/www.fuyao-quartz.com\/wp-content\/uploads\/2026\/03\/3fused_quartz_windows_high_purity_optical_transmission_components-100x100.jpg 100w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">2. Classification of Fused Silica Manufacturing Methods<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">2.1 Natural Fused Silica<\/h3>\n\n\n\n<p>Natural fused silica is produced by melting naturally occurring quartz crystals or silica sand, followed by rapid cooling to form an amorphous structure.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Core principle:<\/h4>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>Direct melting of natural silica \u2192 glass formation via quenching<\/p>\n<\/blockquote>\n\n\n\n<p>Depending on the heat source and process configuration, three primary methods are used:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Electric fusion (industrial mainstream)<\/strong><\/li>\n\n\n\n<li><strong>Flame fusion (oxyhydrogen melting)<\/strong><\/li>\n\n\n\n<li><strong>Plasma melting<\/strong><\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Key characteristics:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Relatively low hydroxyl (OH) content<\/li>\n\n\n\n<li>Higher metallic impurity levels (dependent on raw material purity)<\/li>\n\n\n\n<li>Suitable for industrial and structural applications<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2.2 Synthetic Fused Silica<\/h3>\n\n\n\n<p>Synthetic fused silica is produced from <strong>silicon-containing chemical precursors<\/strong> (e.g., silicon tetrachloride, silane, organosilicon compounds) through controlled chemical reactions.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Core principle:<\/h4>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>Chemical reaction \u2192 formation of ultra-pure SiO\u2082 \u2192 densification<\/p>\n<\/blockquote>\n\n\n\n<p>Based on reaction mechanisms, the main synthesis routes include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Thermal oxidation processes<\/strong> (dry environment oxidation)<\/li>\n\n\n\n<li><strong>Kemiallinen plasmah\u00f6yrypinnoitus (PCVD)<\/strong><\/li>\n\n\n\n<li><strong>Flame Hydrolysis Deposition (FHD)<\/strong> <em>(most widely used)<\/em><\/li>\n\n\n\n<li><strong>Sol\u2013gel processing (wet chemical route)<\/strong><\/li>\n<\/ul>\n\n\n\n<p>Among these, <strong>FHD<\/strong> is the most mature and industrially dominant technology.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">3. Flame Hydrolysis Deposition (FHD): Core Industrial Technology<\/h2>\n\n\n\n<p>FHD can be further divided into two distinct approaches depending on deposition and densification strategies:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3.1 Direct Deposition Method (Ingot Formation)<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>High-temperature hydrolysis produces <strong>molten SiO\u2082 particles<\/strong><\/li>\n\n\n\n<li>Particles are directly deposited onto a substrate<\/li>\n\n\n\n<li>Cooling leads to <strong>bulk fused silica ingots<\/strong><\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Equivalent industrial concept:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Often referred to as <strong>Kemiallinen h\u00f6yrystys (CVD)<\/strong> in ingot manufacturing context<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Applications:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Large-size fused silica blocks<\/li>\n\n\n\n<li>Optical components and structural materials<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">3.2 Indirect Deposition Method (Soot Process)<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Low-temperature hydrolysis forms soot-like SiO\u2082 particles<\/li>\n\n\n\n<li>Particles deposit into a <strong>porous pre<\/strong>f<strong>orm<\/strong><\/li>\n\n\n\n<li>Followed by:\n<ul class=\"wp-block-list\">\n<li>Dehydration (OH removal)<\/li>\n\n\n\n<li>Doping (if required)<\/li>\n\n\n\n<li>High-temperature sintering<\/li>\n\n\n\n<li>Controlled cooling<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Representative technologies:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Two-step CVD process<\/li>\n\n\n\n<li>Vapor Axial Deposition (VAD)<\/li>\n\n\n\n<li>Outside Vapor Deposition (OVD)<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Applications:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Optical fiber preforms<\/li>\n\n\n\n<li>High-purity optical materials<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">4. Key Manufacturing Processes in Detail<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">4.1 Electric Fusion Method (Natural Silica Core Process)<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">Process steps:<\/h4>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Quartz powder is heated using resistance or induction heating<\/li>\n\n\n\n<li>Temperature reaches ~1723 \u00b0C to form molten silica<\/li>\n\n\n\n<li>Melt is rapidly cooled to achieve glassy structure<\/li>\n<\/ol>\n\n\n\n<p>During heating, quartz undergoes phase transitions:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u03b2-quartz \u2192 \u03b1-quartz \u2192 \u03b1-cristobalite \u2192 amorphous silica<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Critical control conditions:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>High vacuum environment (<strong>0.1\u201310 Pa<\/strong>) to remove gas inclusions<\/li>\n\n\n\n<li>Pre-drying of raw materials to minimize moisture<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Characteristics:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Low OH content<\/li>\n\n\n\n<li>Higher metallic impurities (difficult to eliminate)<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">4.2 Two-Step CVD Process (Improved Synthetic Route)<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">Background:<\/h4>\n\n\n\n<p>Traditional one-step FHD processes involve water vapor, leading to high and difficult-to-control OH content. The two-step CVD method addresses this limitation.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Step 1: Porous SiO\u2082 Preform Formation<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Silicon precursors (e.g., SiCl\u2084 or organosilicon compounds)<\/li>\n\n\n\n<li>React in oxyhydrogen flame<\/li>\n\n\n\n<li>Generate <strong>soot-like SiO\u2082 particles<\/strong><\/li>\n\n\n\n<li>Deposit into a porous amorphous structure<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Step 2: Sintering and Densification<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Preform transferred to high-temperature furnace<\/li>\n\n\n\n<li>Dehydration gas introduced to remove OH groups<\/li>\n\n\n\n<li>Sintering and cooling produce dense fused silica<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Key advantages:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Extremely <strong>high purity (minimal metal contamination)<\/strong><\/li>\n\n\n\n<li><strong>Low hydroxyl content (controllable dehydration)<\/strong><\/li>\n\n\n\n<li>Superior performance in:\n<ul class=\"wp-block-list\">\n<li>Deep ultraviolet (DUV) transmission<\/li>\n\n\n\n<li>High-power laser applications<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Raw material considerations:<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>SiCl\u2084 route<\/strong>: mature but produces corrosive by-products (e.g., HCl)<\/li>\n\n\n\n<li><strong>Organosilicon route (e.g., D4)<\/strong>: cleaner but less industrially dominant<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">4.3 Thermal Re-Shaping Process (Post-Forming Technology)<\/h3>\n\n\n\n<h4 class=\"wp-block-heading\">Application:<\/h4>\n\n\n\n<p>Used to fabricate <strong>specific geometries<\/strong> such as:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Quartz tubes<\/li>\n\n\n\n<li>Quartz rods<\/li>\n\n\n\n<li>Precision structural components<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Process principle:<\/h4>\n\n\n\n<p><strong>Heating stage:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Induction heating generates electromagnetic fields<\/li>\n\n\n\n<li>Heat is transferred to the silica material, causing softening<\/li>\n<\/ul>\n\n\n\n<p><strong>Forming stage:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Material is shaped via:\n<ul class=\"wp-block-list\">\n<li>Drawing (pulling)<\/li>\n\n\n\n<li>Controlled sinking or molding<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p><strong>Control parameters:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Furnace temperature distribution<\/li>\n\n\n\n<li>Drawing speed<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Quality-critical factor:<\/h4>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>Uniform temperature field inside the furnace directly determines dimensional accuracy and structural integrity.<\/p>\n<\/blockquote>\n\n\n\n<h2 class=\"wp-block-heading\">5. Comparative Insights: Natural vs Synthetic Fused Silica<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Aspect<\/th><th>Natural Fused Silica<\/th><th>Synthetic Fused Silica<\/th><\/tr><\/thead><tbody><tr><td>Raw material<\/td><td>Natural quartz<\/td><td>Chemical precursors<\/td><\/tr><tr><td>Puhtaus<\/td><td>Kohtalainen<\/td><td>Ultra-high<\/td><\/tr><tr><td>OH content<\/td><td>Matala<\/td><td>Controllable (can be ultra-low)<\/td><\/tr><tr><td>Metal impurities<\/td><td>Higher<\/td><td>Eritt\u00e4in alhainen<\/td><\/tr><tr><td>Kustannukset<\/td><td>Alempi<\/td><td>Higher<\/td><\/tr><tr><td>Sovellukset<\/td><td>Industrial, thermal<\/td><td>Optical, semiconductor, photonics<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">6. P\u00e4\u00e4telm\u00e4t<\/h2>\n\n\n\n<p>The manufacturing of fused silica has evolved from simple quartz melting techniques to highly controlled chemical synthesis processes. While natural fused silica remains important for cost-sensitive and structural applications, synthetic fused silica dominates high-end optical and semiconductor fields due to its superior purity and controllable properties.<\/p>\n\n\n\n<p>Among all technologies, Flame Hydrolysis Deposition (FHD) and its derivative processes play a central role in modern production, especially for applications requiring:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ultra-low impurity levels<\/li>\n\n\n\n<li>Precise optical performance<\/li>\n\n\n\n<li>High reliability under extreme conditions<\/li>\n<\/ul>\n\n\n\n<p>Future advancements will continue to focus on purity enhancement, defect reduction, and process stability, enabling fused silica to meet the increasing demands of next-generation photonic and semiconductor systems.<\/p>","protected":false},"excerpt":{"rendered":"<p>1. Introduction Fused silica (SiO\u2082) is a critical material widely used in optics, semiconductors, and high-temperature engineering due to its exceptional purity, thermal stability, and optical performance. Its manufacturing technologies can be broadly classified into two major categories: natural fused silica and synthetic fused silica. The fundamental distinction lies in raw material sources, which subsequently [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2341,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[819,820,544,563,821,817,815,814,816,68,75,818,822,527,525],"class_list":["post-2688","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industry-news","tag-chemical-vapor-deposition-cvd-silica","tag-flame-hydrolysis-deposition-fhd","tag-fused-quartz","tag-fused-silica","tag-high-purity-silica-materials","tag-low-oh-fused-silica","tag-natural-fused-silica","tag-optical-fused-silica","tag-plasma-cvd-pcvd-silica","tag-quartz-glass","tag-semiconductor-quartz-materials","tag-silica-glass-manufacturing-process","tag-silica-optical-materials","tag-sol-gel-silica-glass","tag-synthetic-fused-silica"],"_links":{"self":[{"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/posts\/2688","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/comments?post=2688"}],"version-history":[{"count":1,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/posts\/2688\/revisions"}],"predecessor-version":[{"id":2689,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/posts\/2688\/revisions\/2689"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/media\/2341"}],"wp:attachment":[{"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/media?parent=2688"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/categories?post=2688"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fuyao-quartz.com\/fi\/wp-json\/wp\/v2\/tags?post=2688"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}