Confinement effects in sesquioxydes

When the size of a particle is decreased to nano-scales, confinement effects induce strong changes. The luminescence of Eu3+-doped Gd2O3 nanoparticles has been studied as a function of both the temperature and the size of the nanoparticles. Two consequences of the small sizes in Eu3+-doped Gd2O3 are observed. First the linewidth of the Eu3+ transitions are inhomogeneously broadened at low temperature, and second the population of the ground and the first excited state of Eu3+ as a function of temperature differs depending on the size: at low temperatures, the smaller the particles, the less populated the first excited state is. The explanation of this second phenomenon could be the absence of very low-energy phonons in small particles.