The synthesis and luminescent properties of morphology-controlled Gd2O3:Dy3+/Eu3+ phosphors with enhanced red emission via energy transfer

Abstract

The red phosphors of Gd2O3:Dy3+/Eu3+ system with nanorod and nanotube morphologies, have been obtained by calcining the precursor in the temperature range of 600–1300 °C for 4 h, and the precursors are synthesized via the hydrothermal method (pH= 8.0–12.0, hydrothermal temperature: 120–180 °C). The phase evolution, controlled-morphology and fluorescent properties were systematically discussed by the various instruments of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence excitation (PLE) and photoluminescence (PL) spectroscopy and fluorescence decay analysis. By changing the synthesis pH and temperature, the phosphor morphology and size could be controlled, and the formation mechanism was analyzed together. The PL spectra of (Gd0.992-xDy0.008Eux)2O3 phosphors shows the strongest red emission (5D0→7F2 transition of Eu3+) under ~275 nm wavelength excitation (8S7/2→6IJ intra f-f transition of Gd3+). The color coordinates of (Gd0.992-xDy0.008Eux)2O3 phosphors were (~0.65, ~0.34), and thus emit the vivid red color emission. The intensity of Eu3+ emission increased with the calcined temperature (600–1300 °C) and Eu3+ content increasing to 4.0 at% (x = 0.04), while the intensity of Dy3+ emission steadily decreased proving the indirectly Dy3+→Eu3+ energy transfer. Compared to the Y2O3 or Gd2O3 doped singly with Eu3+ system, the Gd2O3:Dy3+/Eu3+ phosphor developed in this work displays the much higher red emission at 611 nm (5D0→7F2 transition of Eu3+) ascribed to the efficient Dy3+→Eu3+, Gd3+→Eu3+, Gd3+→Dy3+→Eu3+ energy transfer, and the former Dy3+→Eu3+ energy transfer efficiency was calculated. The luminescent properties (PLE/PL intensity, lifetime, quantum yield, etc.) are strongly dependent on the phosphor morphology, and the related discussion is performed in this work. The Gd2O3:Dy3+/Eu3+ phosphors with changed morphology, enhanced red emission and good thermal stability are expected to be widely used in light and displays area.