Gd<sub>2</sub>O<sub>3</sub>:Eu System: Structural Study of the Influence of Luminescence Center Concentration

Abstract

In this paper, the influence of the Eu 3+ center concentration on the structural and morphological properties of the Gd203 system obtained by Spray Pyrolysis have been studied. The processing route includes aerosol formation by means of ultrasonic device (resonant frequency ranging of 2.1MHz) from common gadolinium and europium nitrate solutions and control over the process of the aerosol decomposition in a medium-temperature (700°C). During the process, spherical, solid, agglomerate-free, submicronic particles with a mean particle size below 800nm and with the crystallite sizes below 20nm were obtained. In order to control the particles crystal structure and to establish the conditions for the stabilization of the low-temperature gadolinia cubic phase, the process parameters like temperature distribution, gas flow rate and annealing temperatures were adopted. The nanoparticle morphology, crystalline and chemical structure were studied by XRD, SEM and EDS. TEM has been applied in order to characterize this system. The low magnification bright field images permit to identify the structure and the growth small primary nanoparticles through the collision/coalescence mechanisms. HRTEM permits to determine the presence of domains locally affected by Moires Frames and Crystallite Size. The selected electron diffraction patterns area allow determining the presence of a polycrystalline material with two phases in the as-prepared samples, and only a Ia3 phase along the thermal treatment. The obtained results and the mechanisms of ultrafine phosphor particles generation were discussed in terms of precursor chemistry, process parameters and structural characteristic.