| CPC C01B 33/193 (2013.01) [C01P 2002/02 (2013.01); C01P 2002/54 (2013.01); C01P 2002/88 (2013.01); C01P 2004/04 (2013.01); C01P 2004/64 (2013.01); C01P 2006/12 (2013.01)] | 12 Claims |

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1. An amorphous silica powder comprising boron atoms,
the amorphous silica powder having an average particle size in a range from 10 to 100 nm, as determined from 40 particles selected at random in a transmission electron micrograph,
the amorphous silica powder having a decrement in a boron content in a range of 10 mass % or less, when fired under following conditions:
5 to 10 g of a dried product of the amorphous silica powder is filled into an alumina crucible, heated in an atmosphere at 200° C./hour to a temperature in a range from 1000° C. to 1100° C., maintained as is for 5 hours, and cooled to room temperature,
wherein the decrement is determined by a formula below:
the decrement (%)=(B2O3 content in the dried product of the amorphous silica powder−B2O3 content in a fired product of the amorphous silica powder)/(the B2O3 content in the dried product of the amorphous silica powder)×100.
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