примесь

см. тж. беспримесный; добавлять примесные элементы; с примесью

Tellurium atoms were introduced as a dopant.

Emery is a greyish black variety of corundum containing much admixed magnetite or hematite.

Many impurities in the aggregate are lighter than the good stone or sand.

Источник: Русско-английский научно-технический словарь на Gufo.me