Elan 46 LAS Glass Ceramic for Modern Glass-To-Metal Sealing

Elan Technology

Advanced Hybrid Glass Ceramic Technology


Elan 46 is a specialty belt process lithia-alumina-silica (LAS) glass-ceramic for use sealing to a wide range of metals with varied coefficients of thermal expansion (CTE) such as nickel-based Inconel or Hastelloy and stainless steel alloys. The Elan 46 LAS chemistry is specifically designed for a single ‘hump’ belt thermal profile whereby a preform is heated sufficiently to a melt glass which is capable of crystallizing lithium phosphate and upon cooling creating cristobalite nuclei. During a controlled cooling rate to an appropriate temperature the crystallization of lithium silicates and growth of cristobalite occurs so that the CTE can be tailored up to a high of approximately 200×10−7 in/in/°C.[1]

The ceramic technology used in glass-ceramics (G-C) are especially useful in glass-to-metal (G/M) sealing due in part to their ability to exhibit key properties of both a glass hermetic seal and a ceramic seal:

  • Formability: The ability to flow the molten 46 glass into a complex geometry and then crystallize make it ideal when complex geometries are required.
  • Hermeticity: The chemistry of Elan 46 lends itself to developing a strong chemical bond between the glass-ceramics and metal constituents. This bond may enhance both the strength and hermeticity of the seal, depending upon the production parameters.
  • Strength: The ability of Elan 46 to crystallize during a simple belt process thermal profile contributes to the strength of the overall bulk glass.
  • CTE Customization: The degree of crystallization of the ceramic phase(s) and morphology of Elan 46 drives the desirable ability to adjust the CTE according to the constituent material system.
  • Production: Utilizing Elan 46 glass-ceramics instead of a traditional ceramic seal removes the need of an additional interlayer and accompanying production step.
  • Durability: Elan 46 is a robust glass-ceramics capable of withstanding greater operational temperatures compared to conventional glass seals and is resistant to chloride attack.

2-D Transverse Hardness Map of Crystallized Bulk Elan 46 Ceramic Technology

Fig 1. 2-D Transverse Hardness Map of Crystallized Bulk Elan 46
The lighter hue polymorph is illustrative of a harder crystalline phase.

Crystallization Study

A crystallization study was performed to detail the nanomechanical properties of Elan 46, a LAS glass-ceramic, as a result of thermal processing.[2] A transverse 2-D hardness map of bulk Elan 46 with accompanying histogram were produced based on a typical belt furnace heat treatment: Rise to 980°C, flowed, and control cooled to allow crystallization.

Nanoindentation makes it possible to quantify intrinsic material properties of highly heterogeneous bulk materials or interfaces on a sub-microscale resolution and upscale the characterization to a real world macroscale application.

The hardness results from 1600 discrete nanoindentation sites manifest a bimodal distribution, signifying mechanically that a harder crystalline phase is present as well as a glass phase. Viewing 1600 hardness measurements as either a map or a histogram clarifies a distinction in bulk properties of the sub-microscale Elan 46 G-C that would be obscured with only 10–15 Vickers measurements.

Chart 1. Bimodal Hardness Histogram of Crystallized Elan 46 Ceramic Technology

Chart 1. Bimodal Hardness Histogram of Crystallized Elan 46


High strength glass-ceramics, as illustrated here mechanically, feature the benefit of strengthening through crystallization of a second phase. This study documents an increase in degree of crystallization with less retained glass and overall crystal growth due to thermal processing. When working with G-C/M seals it is generally the goal to develop a higher strength via. a higher degree of crystallization with less retained glass and without coarsening the grains or significantly shifting the overall hardness to make the seal overly brittle.

Glass-Ceramic Composites from Elan Technology, Inc.

Elan Technology is a leader in the technical glass, ceramic technology and contract spray drying industries. Elan Technology is the largest independent U.S. Company in its field producing glass preforms for hermetic seals and spacers using technical glass, ceramics, and glass-ceramic composites. Our line of colored glasses are used by artists around the world in their glass sculptures and creations. Since 1998, when we were first registered under the QS-9000 standard, we have continued to develop and improve our quality system. As our businesses have evolved, we are pleased to announce that we have transitioned to ISO 9001:2015.


[1] 46 Glass/Ceramic | ElanTechnology.com. Ceramic Glass Composite Material. Web. 6 Apr.2015

[2] . Dissertation, Clemson University. Ann Arbor: ProQuest/UMI, . (Publication No. AAT 3680707.)

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