Luminescence of CNT coated LaPO4:Tm phosphors and their field emission lamp application

• CNT coating increased atomic concentrations of O and C by 27.4% and 9%, respectively.
• Wavelengths of the CL and PL peaks were the same, neither was altered by CNT coating.
• CL intensity was enhanced by a factor of 3.86 when CNT coating was used.
• PL intensity decreased severely by CNT coatings.

When the phosphor LaPO4:Tm was coated with carbon nanotubes (CNTs), carbon atoms were diffused into the phosphor lattice. Binding energy of La 3d and C 1s were not shifted by CNT coating, while that of O 1s was lowered slightly as a result of the formation of CO and CO bonds on the phosphor surface. CNT coating increased the atomic concentrations of O and C by 27.4% and 9%, respectively. Photoluminescence intensity decreased significantly, by 52%, when CNT concentration of 1.5 wt% was coated. This is attributed to covering the phosphor with black CNTs/carbons and the formation of CO and CO bonds on the phosphor surface. Conversely, cathodoluminescence (CL) intensity was improved by a factor of 3.86 when 1.25 wt% of CNTs was coated, attributing to improved conductivity, reduced charging, and increased CL excitation probability of the phosphor. The influence of CNT coating on the luminescence of LaPO4:Tm was compared with that of LaPO4:Eu phosphor. Blue CL was observed from LaPO4:Tm, it is potential for field emission lamp application.