Phase transformation and morphology tuning of β-NaYF4:Yb3+,Er3+ nanocrystals through K+ ions codoping |
XRD patterns of the nanocrystals codoped with different contents of K+ ions and the standard data of β -NaYF4 (JCPDS No. 16-0334) and β -KYF4 (JCPDS No. 27-0466). |