The spectroscopic quality factor, phase, morphological, structural, and photoluminescent analysis of ZrO2:Nd3+ coatings created by Plasma electrolytic oxidation

15 mu m thick ZrO2:Nd3+ coatings were synthesized by the plasma electrolytic oxidation process from the pure zirconium substrate in an alkaline electrolyte with the addition of five different concentrations of Nd2O3 pow-ders. SEM/EDS images show morphologies characterized by numerous pores and cracks, and uniform distribu-tion of coating constituents. XRD revealed that the monoclinic phase is dominant and that Nd impurity stabilizes the tetragonal phase. The average crystalline size is 27.5 nm. XRF revealed a linear increase in incorporated Nd with increasing Nd2O3 concentration. Photoluminescence spectra are characterized by the NIR emissions at typical energies for Nd3+ ion. The highest emission intensity is obtained with 2.0 g/L Nd2O3. The explicit equation for branching ratios in relation to the emission intensities and Judd-Ofelt parameters is recalculated. A novel, more precise equation for the calculation of the spectroscopic quality factor from the most intense emissions is presented. The spectroscopic quality factor is the lowest in the sample with the highest photo -luminescent intensity, and is one of the lowest values, in comparison with the 203 spectroscopic quality factors calculated from the Judd-Ofelt parameters in the literature. The luminescence intensity decreases with tem-perature by the phonon-assisted cross-relaxation mechanism. The luminescence thermometry by the lifetime of F-4(3/2) level shows similar to 2% K-1 relative sensitivity in the 300-380 K temperature range.

Automated summary

In this study, 15 μm thick ZrO2:Nd3+ coatings were synthesized using the plasma electrolytic oxidation process with the addition of different concentrations of Nd2O3 powders. The coatings exhibited morphologies characterized by numerous pores and cracks, with uniform distribution of coating constituents. The XRD analysis revealed the dominant monoclinic phase and the stabilization of the tetragonal phase by Nd impurity. The Nd2O3 concentration was found to have a linear effect on the incorporation of Nd in the coatings. Photoluminescence spectra showed near-infrared emissions at typical energies for Nd3+ ion, with the highest emission intensity observed at 2.0 g/L Nd2O3. A novel equation for calculating the spectroscopic quality factor from the most intense emissions was presented, showing that the coating with the highest photoluminescent intensity had the lowest spectroscopic quality factor. The luminescence intensity decreased with temperature due to the phonon-assisted cross-relaxation mechanism, and luminescence thermometry showed a relative sensitivity of about 2% K-1 in the temperature range of 300-380 K.