The Properties of Upconversion Luminescence on YAlO₃:Er³⁺ Nanophosphors with Different Er³⁺ Concentrations

We report the properties of upconversion luminescence on Yttrium aluminum perovoskite (YAlO₃) doped with trivalent erbium at concentrations of 1, 2, 3, 5 and 7 mol%. The samples were synthesized by solvo-thermal reaction method and the XRD patterns conforms that the YAP:Er³⁺ nanophosphors have orthorhombic phase. Efficient green and red upconversion (UC) emission of YAP:Er³⁺ nanophosphors was measured under the excitation of 975 nm continuous wave diode laser, and its dynamics and pump power dependence were investigated. As concentration of Er³⁺ ion increased from 1 to 7 mol%, the red UC emission increased more rapidly. It is attributed to the energy transfer (⁴I_11/2→⁴I_15/2:⁴I_13/2→⁴F_9/2) and to the cross relaxation (⁴S_3/2→⁴I_9/2:⁴I_15/2→⁴I_13/2) between Er³⁺ ions. In this case, the green and red emissions were yielding from quadratic to linear. These conclusions obtained are confirmed by theoretical investigations based on steady-state rate equations.