The peculiarities of light absorption and light emission in Cu-doped Y-stabilized ZrO2 nanopowders

The influence of doping with copper and annealing temperature on the characteristics of yttrium-stabilized ZrO2 nanopowders was investigated using photo- and cathodoluminescence as well as diffuse reflectance and electron paramagnetic resonance methods. After annealing at temperatures below 800 degrees C, both Cu-doped and Cu-free powders demonstrate light emission in the blue-red spectral range that are characteristic of the tetragonal ZrO2 phase. In the excitation spectra of blue-orange photoluminescence it was found a maximum in the range of light absorption by oxygen vacancies, indicating that the corresponding emitting centers are vacancy related complexes. A red luminescence band was found to be excited only by the light from band-to-band ZrO2 absorption. It was observed that the increase of annealing temperature up to 1000 degrees C stimulates the appearance of additional luminescence bands at similar to 510 and 580nm correlated with the formation of monoclinic ZrO2 phase. The corresponding emitting center is considered to be a substitutional copper ion, the excitation of which can occur both via the capture of free carriers and via the energy transfer from oxygen vacancies.