Thermal properties. Temperature-dependent normalized emission intensities for (a) (Ca1-x
)N3:Eu and (b) (Ca1-x
)N3:Eu samples (x = 0 – 0.15). These curves are fitted by I
0 = [1 + D exp(−E
a/kT)]−1. Photoluminescence spectra were obtained at T = 298 K to 573 K, and is shown in the right hand side. (c) Activation energies as a function of variable x for La and Li series. (Reprinted with permission from reference . Copyright 2013, American Chemical Society).