The Infrared Emissivity And Photoluminescence Of Rare Earth Doped Zao Ceramics

Lanthanide rare-earth-doped ZAO ceramics and thin films (ZAOR) were prepared and their infrared emissivity in the 8¹4μm band and photoluminescence properties were investigated. Rare-earth-doped CaO: ZAO monolithic ceramics (ZCAO) were prepared and infrared emissivity and dielectric properties were studied. The light rare earth (Y3+, Ce4+, Pr2+ / Pr3+ and Nd3+) and heavy rare earth (Sm³⁺, Eu³⁺, Gd³⁺, Tb⁴⁺/Tb³⁺, Dy³⁺, Ho³⁺ and Er³⁺) doped ZAO monolithic ceramics were prepared by high-temperature sintering.The content of rare-earth was lower than 0.92at% . Ce4+, Sm³⁺ and Er³⁺ ions reduced the emissivity of ZAO ceramics while the other rare earth increased it.The emissivity of ZAOR ceramics were 0.927⁰.958. Using the UV excitation, all the rare earth ions can enhance green and yellow emission of the ZAO ceramic. The energy transfer from ZnO substrate to rare earth ions was observed, which was due to cross-relaxation process giving rise to the phenomenon of concentration quenching of fluorescence. Ce4+ and Er³⁺ had a special role of enhancing the emission of ZAO ceramic in the visible range, and Er³⁺ green emission was observed with the split-level phenomena.Using RF magnetron sputtering, Dy³⁺, Ho³⁺ and Er³⁺-doped ZAO films were deposited respectively on aluminum alloy (2024) and quartz glass surface, respectively. The sputtering power, film thickness and the amount of rare earth doped ZAOEr films on quartz glass substrate were discussed to the influence of structure and infrared emissivity in the 8¹4μm-band. Before the heat-treatment, the emissivity of the ZAOR films were 0.810⁰.856, and the heat-treatment reduced the emissivity of quartz glass-based thin-film. The minimum emissivity of ZAOEr film was 0.765 after annealing. The emissivity of Al alloy-based thin-film increased as the film thickness increased, which was 0.169⁰.578. The luminous intensity of ZAOR films was weaker than the monolithic ceramics, and light-emitting mechanism was slightly different. Rare-earth Nd, Ho, Dy and Sm made ZCAO ceramics have a low dielectric constant, high dielectric loss, and enhanced the emission intensity of blue, green and yellow. Sintering temperature and time can increase the dielectric constant of Nd-Ho co-doped ZCAO ceramics and reduce its dielectric loss. ZCAO ceramics were formed by the new phase of CaO, CaAl₂O₄, and CaCO₃ did not degrade completely. At 1250℃for 2 hours, the largest dielectric constants (εr) of Nd-Ho and Dy-Sm-doped ZCAO ceramics were 9.52 and 8.5, respectively. The emissivity of rare-earth doped ZCAO ceramic was 0.955 0.980.