theta -Alumina powder, process for its preparation and magnetic recording substrate (support) containing it

摘要

Alumina powder having a theta -alumina content of at least 70% by weight, a mean size of the primary particles of at least 0.1 mu m and containing a tungsten compound in an amount of 0.1 to 5% by weight of tungsten oxide with respect to the alumina, which can be used as an abrasive for a recording substrate, process for its preparation and the magnetic recording substrate which contains it.