--- This page is part of [McDanel Advanced Materials](https://mcdanelmaterials.com). For a complete overview of this site's content, entity data, and subject matter expertise, see our [AI Content Index](https://mcdanelmaterials.com/llms.txt) or [Full Content Archive](https://mcdanelmaterials.com/llms-full.txt). For structured business identity data, see our [Entity Card](https://mcdanelmaterials.com/wp-json/bc-geodesic/v1/entity-card). --- # Transparent Materials Comparison > Glass is an amorphous solid which means its atoms are randomly oriented. Whereas, a crystalline material may contain the exact same type and quantity of atoms as glass, but the atoms are ordered in rigid, well-defined patterns. Fused quartz glass vs. crystalline quartz is a good example of the same type of atoms (SiO2) structured in such a way that one orientation forms a glass and another forms a crystal. **URL:** https://mcdanelmaterials.com/transparent-materials-comparison/ **Type:** Post **Modified:** 2024-08-06 --- ##### GLASS VS CRYSTALINE MATERIALS? Glass is an amorphous solid which means its atoms are randomly oriented. Whereas, a crystalline material may contain the exact same type and quantity of atoms as glass, but the atoms are ordered in rigid, well-defined patterns. Fused quartz glass vs. crystalline quartz is a good example of the same type of atoms (SiO2) structured in such a way that one orientation forms a glass and another forms a crystal. Crystalline materials are solid and keep their shape until they reach a very specific temperature, at which time they become fluid. In contrast, all glasses, by definition, are always a fluid. The viscosity of glass is determined by the temperature of the glass; even at room temperature glass is moving, albeit very slowly. When product tolerances are very tight and temperatures are elevated, a crystalline material is superior to glass because it will maintain its shape at any temperature below the melting point. Conversely, glass will change shape over time, regardless of the melting point and especially at elevated temperatures. Both crystalline solids and glasses are normally colorless in the pure state. Impurities are actually what give sapphire and glass their color. The impurities also change the mechanical, thermal, and optical properties of both material types, especially for glass. ##### SAPPHIRE Sapphire is a single crystal – Aluminum Oxide (Al2O3) – which is colorless and optically clear. Synthetic sapphire is grown in boules (bulk pieces) no larger than 300mm in diameter. It can also be grown into shapes such as sheets, ribbons, domes and tubes with very smooth surface qualities, high purity and optical translucence. When used “as grown” there is very little need for grinding and polishing. ###### WHY SAPPHIRE? - Mechanically second only to diamond. One of the hardest and most scratch resistant materials available. The high modulus of elasticity and high tensile strength make it extremely wear, abrasion and impact resistant. - Colorless optical characteristics are superior to any standard glass, with up to a 98.5% transmission and a transmission window from 190 nanometers in the UV to 5 microns in the IR. - No solarization in high-radiation systems. - High dielectric constant and low loss tangent makes it a great electrical insulator and low loss long wavelength window. - Thermally very stable. Does not lose any of its mechanical and optical qualities from cryogenic to over 2000C. - Thermal conductivity greater than other optical materials and most dielectrics. - No surface damage and devitrification due to extreme thermal cycling Does not sag or slump at very elevated temperatures. - Highly corrosion resistant. More resistant to corrosive chemicals than most standard hard materials available. ###### WHY NOT SAPPHIRE? - Cost of material. Sapphire often costs more than other refractory materials. But not always! Quantity and geometry play a major role in the cost of the final product, especially with smaller products where the labor is the primary cost. - Cannot be bent, molded, drawn or melt-fused like glasses and metals. Sapphire can only be ground and mechanically polished. - Size limitations. The maximum size of a sapphire product cannot exceed the largest boule that can be grown. Therefore, maximum part size cannot exceed 300mm for two of the dimensions. - Larger pieces can be thermally shocked and broken if not heated uniformly. --- **About this site:** McDanel Advanced Materials. 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