Optical characterization of spherical fine particles of glassy Eu3+ doped yttrium basic carbonates

Spherical fine particles of glassy Eu3+ doped yttrium basic carbonate, whose sizes are about 300 nm in diameter, are prepared by a co-precipitation method using urea as a precipitation generator. The optical properties concerned with the f–f transitions of Eu3+ are investigated for the as-prepared powder and the powder samples calcined at 300 and 550 °C. As the calcination temperature becomes high, the absorption band (charge-transfer band) due to the electron transfer from O2− to Eu3+ shifts to lower energy. The forced electric dipole 5D0–7FJ (J=0,2,3,4) transition strengths and the inhomogeneous width of the 5D0–7F0 luminescence spectrum of Eu3+ increase with calcination temperature. From these results, the local structure around Eu3+ is compared among the three powder samples. The persistent spectral hole burning (PSHB) effect is observed at 10, 70, and 120 K in the 7F0–5D0 transition of Eu3+ in all the samples. It is found that, at these temperatures, the burning reaction rate decreases with increasing calcination temperature. Probable PSHB mechanisms of the three samples are discussed.