Controllable hydrothermal synthesis and photoluminescence properties of CaGd 2 (WO 4 ) 4 :Eu 3+ red‐emitting phosphor

Abstract CaGd 2 (WO 4 ) 4 :Eu 3+ phosphors with controllable morphology were synthesized via the hydrothermal method. The influences of pH value, reaction time and Eu 3+ concentration on the crystal structure, morphology, and photoluminescence properties of CaGd 2 (WO 4 ) 4 :Eu 3+ were studied. The pure tetragonal structure CaGd 2 (WO 4 ) 4 is obtained when the pH value is 8 and 9. Furthermore, by altering the pH value of the reaction solution, the morphologies of the CaGd 2 (WO 4 ) 4 :Eu 3+ phosphors evolve from spindle‐shaped grains to tetragonal plate‐like grains and finally to aggregated bulk particles. Under the 394 nm excitation, the phosphors display a bright red emission corresponding to the characteristic 4 f ‐4 f transitions of Eu 3+ , and the intensity of emission peaks depends mainly on the pH value, the reaction time, and the Eu 3+ concentration. The optimum photoluminescence performance is achieved for CaGd 2‐ x (WO 4 ) 4 : x Eu 3+ ( x = 1) phosphor synthesized at pH = 8 under the reaction time of 16 h. Finally, the thermal stability of the phosphors is analyzed at different ambient temperatures.