Synthesis of ZnO Nanoparticles and Luminescent Doped ZnO Phosphor by Spray Pyrolysis

Abstract

An additive salt, LiNO3, was used as a shield in the preparation of single crystalline ZnO particles via an ultrasonic spray pyrolysis route in order to prevent particle-agglomeration and enhance the crystallinity of the product. LiNO3 was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. Powder X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.
Also using the same apparatus, i.e. ultrasonic spray pyrolysis method, europium doped ZnO (ZnO:Eu) phosphor particle was directly synthesized. The crystal structure of product was designated by europium ions concentration and the synthesis temperature. We identified the coexistence of Eu²⁺ and Eu³⁺ in the as prepared ZnO, which was strongly influenced by the doping concentration and the synthesis temperature. With the addition of 0.5 mol % concentration of europium ion, only Eu²⁺ ion existed in the particles, while both Eu²⁺ and Eu³⁺ ions existed in the particles when using 1 mol % or higher concentration of europium ions. We also found that by changing the wavelength of excitation source, both of blue luminescence and red luminescence can be obtained.