Zn2SiO4:Mn phosphors for plasma display panels (PDP) application were synthesized by large-scale ultrasonic spray pyrolysis process using metal alkoxide precursor. To avoid the formation of irregular-shaped particles owing to the hollowness and phase-segregation characteristics of the silicon component, organic additive, citric acid (CA) was introduced in the spray pyrolysis. The influence of CA addition on the morphological and luminescent characteristics of the Zn2SiO4:Mn phosphor particles was investigated. The amount of CA addition is an important factor in controlling the morphological and luminous characteristics of Zn2SiO4:Mn phosphor particles. The particles prepared from the solution containing an appropriate amount of CA had a completely spherical shape, dense morphology, nonaggregation characteristics, and higher photoluminescence intensity than the commercial product, while those prepared from the solution containing excessive CA had an irregular shape, high porosity, rough surfaces, and lower brightness than the commercial product.