  In this article a new idea is proposed by PKU group to improve the RF
superconductive property of niobium cavity. Rare earth elements like scandium
and yttrium are doped into ingot niobium during the smelting processes. A
series of experiments have been done since 2010, and the preliminary testing
results show that the magnetic property of niobium materials has been changed
with different doping elements and proportions while the superconductive
transition temperature almost does not change. Then a large ingot niobium doped
with scandium was melted. RRR and mechanical properties were measured. This
method may increase the superheating magnetic field and decrease surface
resistance of niobium so as to improve the performance of niobium cavity which
is a key component of SRF accelerators. A single-cell cavity made of Sc-doped
niobium has been fabricated.
