Synthesis Of T’-YSZ Based Fluorescent Material And APS Coatings By Sol-Spray Pyrolysis Process

The difficulty of fluorescence material preparation is enhanced by the low doping concentration of the rare earth luminescent elements and the high sensitivity of the fluorescence intensity to the luminescent element content of the 7-8 wt%Yttria Stabilized Zirconia（YSZ）based non-contact fluorescence thermometry coatings.In this paper,the sol-spray pyrolysis process with accurate and controllable composition,uniform of each component and high purity of t’phase was introduced for the synthesis of the luminescence materials.The composition design and preparation of t’-YSZ:Eu,Dy and Er powders was carried out,and the structural characterization and fluorescence properties of the powders and coatings were investigated.The main results are as follows:（1）Pure t’-YSZ:Eu,Dy and Er powders were designed and prepared.Doped or co-doped zirconia powders of 8.7Y-1Eu,5Y-5Eu,10Eu,8.7Y-1Dy,5Y-5Dy,8.7Y-1Er,7.7Y-2Er,6.7Y-3Er,5.7Y-4Er and 4.7Y-5Er were synthesized by sol-spray pyrolysis process.The results of XRD and Raman characterization and analysis show that no harmful monoclinic phase or cubic phases are found in all the powders,and all of the XRD diffraction peaks and Raman active peaks are consistent with a tetragonal phase structure.（2）The effect of composition on the spectrum of fluorescent powder was studied.The fluorescence intensity did not change significantly at the maximum excitation wavelength of 257 nm and the maximum emission wavelength of 606 nm when the Eu³⁺content was increased from 1 wt%to 5 wt%.However,when the Eu³⁺content was increased to 10 wt%,the fluorescence intensity of the powder decreased significantly.This result indicates that the concentration quenching effect occurs when the Eu³⁺content increases to 10 percent.The results for Dy³⁺doped YSZ are in agreement with those for Eu³⁺doped YSZ.At the maximum excitation wavelength of352 nm,the Dy³⁺content increases from 1 wt%to 5 wt%,and at the maximum emission wavelength of 584 nm,the fluorescence intensity changes little.The fluorescence intensity at the maximum emission wavelength of 584nm shows little change when the content of Dy³⁺increased from 1 wt%to 5 wt%.The fluorescence material doped with Er³⁺is significantly different from Dy³⁺and Eu³⁺.The fluorescence intensity is highly sensitive to the content of Er³⁺dopant content.When the Er³⁺content increased from 1 wt%to 5 wt%and at the maximum excitation wavelength is 517nm,the fluorescence intensity at the maximum emission wavelength of 544 nm is,gradually decreases with the increase of doping content.The maximum emission intensity of8.7Y-1Er is much higher than that of the other doped contents.（3）The crystal structure and fluorescence characteristics of the fluorescent coating prepared by air plasma spray（APS）process were studied.The YSZ coatings doped with 1 wt%Eu and 5 wt%Eu,1 wt%Dy and 5 wt%Dy and 1 wt%Er were prepared by APS process,respectively.The XRD results show that the crystal structure of the coating is consistent with the powder,with no significant change in the crystal lattice constant.The fluorescence spectra of the coatings are consistent with those of the powder.The crystal structure and fluorescence spectra of the coating did not change even after heat treatment at 1400℃.In summary,a pure T-phase YSZ based fluorescent material has been successfully fabricated by a sol-spray pyrolysis process,which not only broadens the composition range,but also ensures the consistency of the coating and powder in terms of crystal structure and fluorescence properties.This lays the foundation for the application of the non-contact fluorescence calorimetry coating technique in aero-engines.