Thermal conductivity against densityHigher and further left: spreads more heat for its weightThermal expansion against thermal conductivityLower and further right: warps less when heated
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Sources2 documents: Pilkington North America, Korth Kristalle
Glass
Annealed soda-lime-silica float glass, Pilkington North America Technical Bulletin ATS-129 (04/2025)
Silicon
Synthetic single-crystal silicon (cubic, diamond structure), Korth Kristalle (crystal grower) material data; Korth usually supplies Floating Zone (FZ) material, Czochralski (Cz) also offered. Silicon is elastically anisotropic; the producer quotes one modulus and the solver is isotropic.
1
Technical Bulletin ATS-129: Properties of Soda-Lime Silica Float Glass (2025)Pilkington North Americaarchived copyGlass · Ultimate tensile strength: typical mean surface tensile stress at fracture (MOR), 60 s load, weathered, 50% breakage probabilityGlass · Flexural strength: mean MOR (same value as tensile)Glass · Young's modulus (stiffness): typicalGlass · Density: typicalGlass · Poisson's ratio: typicalGlass · Thermal conductivity: typical at 75 FGlass · Thermal expansion: typical, 75-575 FGlass · Specific heat: typical at 75 FGlass · Max service temperature: strain point (ASTM C336) - stress-relaxation onset, not a rated service limit
2
Si: SiliconKorth Kristallearchived copySilicon · Ultimate tensile strength: modulus of rupture (bending fracture stress); brittle, no yield pointSilicon · Flexural strength: modulus of ruptureSilicon · Young's modulus (stiffness): typical (single quoted value of an anisotropic crystal)Silicon · Density: typicalSilicon · Poisson's ratio: typicalSilicon · Thermal conductivity: typical at 313 K (40 °C)Silicon · Thermal expansion: typical at 300 KSilicon · Specific heat: typicalSilicon · Melting point: typicalSilicon · Max service temperature: producer's maximum application temperature (optical components)
Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Questions
Mechanical
Is Glass stronger than Silicon?
Silicon is stronger: its tensile strength is 130 MPa against 41 MPa for Glass (3.17x).
Which is lighter, Glass or Silicon?
Silicon is lighter: 2,329 kg/m³ against 2,500 kg/m³ for Glass.
Which is stiffer, Glass or Silicon?
Silicon is stiffer: Young's modulus 131 GPa against 72 GPa for Glass, so the same part in Silicon deflects less under the same load.
Which is lighter for the same job, Glass or Silicon?
For the same stiffness or strength: Silicon is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Glass
Silicon
Stiff rod or tie (tension)
1.95x heavier
lighter
Stiff beam (bending)
45% heavier
lighter
Stiff panel or plate
31% heavier
lighter
Strong rod or tie
3.4x heavier
lighter
Strong beam
2.32x heavier
lighter
Strong panel or plate
1.91x heavier
lighter
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).
Thermal
Which conducts heat better, Glass or Silicon?
Silicon conducts heat better: 163 W/m·K against 0.937 W/m·K for Glass.
Which expands less with temperature?
Silicon expands less: 2.62 µm/m·K against 8.3 µm/m·K for Glass.