A selective replacement strategy to a deep-red phosphor for plant growth and optical temperature sensing

For the absorption of plants, it is important to synthesize phosphors with emission bands in the red region. Herein, a series of new red phosphors Sr1-xLa2+xAl2-xO7: xMn4+ (SLA: xMn4+) were synthesized by the high temperature solid-state reaction. The inconsistent charge number of Mn4+ dopant and substituted Al3+ ion can be compensated by manual adjusting of the proportion of Sr2+ and La3+ in the same crystallography site. The phosphor shows emission band at around 713 nm, which fits well with the absorption of Pfr (far-red light-absorbing phytochrome), meaning that the SLA: 0.006Mn4+ can promote plant growth. Furthermore, co-doped phosphor SLA: 0.006Mn4+, 0.006Dy3+ was prepared with interesting temperature-dependent luminescence. With temperature increasing, the emitting intensity of Mn4+ has a more pronounced decline in comparison with Dy3+. Due to this feature, SLA: 0.006Mn4+, 0.006Dy3+ can be used as a non-contact optical thermometer with Sa of 0.018 K−1 at 450 K and Sr of 1.458% K−1 at 425 K.