| http://www.w3.org/ns/prov#value | - Therefore, the content of ZnO is preferably more than 0%, but not more than 5%, morepreferably 0.5 to 5%, still more preferably 1 to 5%.ZrO.sub.2 is a component for producing a high refractive index, and when added in a small amount, it has an effect that the glass is improved in devitrification resistance.
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