Photoluminescence properties of La3+-doped BaY1.94Eu0.06ZnO5 phosphor prepared using a sol-gel method

The La3+-doped BaY1.94Eu0.06ZnO5 nano-crystal phosphors were prepared using a sol-gel method. The x-ray diffraction profiles show all of the peaks are attributed to the BaY2ZnO5 phase when co-doped with the (La3+, Eu3+) ions. The broad band centered at 301 nm and the sharp peaks from 320 to 410 nm are attributed to the charge transition state (CTS) from O2− to Eu3+ ions of the host lattice and the intra-4f forbidden transitions of Eu3+ ion, respectively. Under an excitation of 395 nm, the emission spectra of BaY1.94−xLaxEu0.06ZnO5 samples exhibit a series of shaped peaks assigned to the 5D0→7FJ (J=0, 1, 2, 3, and 4) transitions. Luminescence from the higher excited states, such as 5D1, 5D2, and 5D3, was also observed, even though the La3+ concentration was up to x=0.36. In the BaY1.94−xLaxEu0.06ZnO5 system, a different La3+ concentration did not change the locations of these excitation and emission peaks, but did change the intensities of them. The intensities of excitation and emission peaks increase and then decrease, when the La3+ ion concentrations are increased, and the maximum intensities for both the peaks occur when x is 0.28. This is due to the lattice distortion and induces an increase in the degree of compressive strain, which causes the amount of oxygen vacancies to decrease when La3+ substitutes the Y3+ ion.