To provide a hexagonal zirconium phosphate-based low thermal expansion filler which is excellent in productivity and heat resistance stability and is further effective in adjusting the thermal expansion of a sealing material that is also excellent in processability, and to provide a glass composition using it.

The low thermal expansion filler is characterized in that it is comprised of hexagonal zirconium phosphate that is synthesized by a wet method or a hydrothermal method, and the glass composition is one that contains the low thermal expansion filler.

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