Luminescence of alumina ceramic doped with lanthanum under medium- and high-dose irradiation

La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

“…121 In agreement with this mechanism, the reaction slows down in an inert atmosphere (N 2 or Ar). 121,394 Nevertheless, Zvonarev et al 238 achieved higher LHA yields by calcination in vacuum than by calcination in air. A reason for this observation was not given.…”

“…Higher surface areas are clearly seen for samples prepared in microemulsions (entries 54–58) ,,− (e.g., 67 m 2 /g in entry 58). Further methods to obtain LHA include precipitation (as opposed to coprecipitation, entry 26), solid-state reactions (entries 1–6), ,,,,,− ion-exchange or impregnation of aluminas or alumoxane with decomposable La-salts (entries 7–14), ,, , , , ,, Pechini method (entries 15, 17, 18), , , , carbon templating (entries 19–21), , , , as well as combustion and oxidation routes (entries 22–25). , , , With respect to surface areas, only a combined Pechini/carbon-templating route (entry 18, 90 m 2 /g) can compete with synthesis in microemulsions. Remarkably, in none of the entries in Table S1, a molar Al/La ratio of 14.2, corresponding to the genuine Al/La ratio in LHA, is used in the starting material.…”

“…It is also a good host material for a variety of guest ions, and both the A and B sites can be doped with a wide choice of other metal ions. This opens the doors to an extended range of possible applications; i.e., as photo- and/or thermo-luminescent materials, − specifically after doping with RE ions. ,− In this way, LMA finds applications in dosimeters for UV and ionizing radiation, and for the color adjustment of light-emitting diodes (LEDs). LMA doped with Mn 4+ has attracted particular attention due to its intense emission in the red and near IR region .…”

“…Generally, the crystallinity (and the yield) of LHA increases with increasing calcination temperature. , , ​ , , ​ , ​ , ​ , − However, elevated temperatures are expected to trigger grain growth, resulting in increased crystal sizes and reduced surface areas. , Therefore, the search for synthetic procedures that keep the calcination temperature as low as possible, is an ongoing task. Even for unstabilized, that is, unsubstituted La- or Ba-HA, formation temperatures below 1200 °C are occasionally reported.…”

“…It was concluded that the conversion of O 2 to O 2– at the phase boundary of the growing LHA is the rate-limiting step, accompanied by diffusion of a metal ion (Al 3+ or La 3+ ) . In agreement with this mechanism, the reaction slows down in an inert atmosphere (N 2 or Ar). , Nevertheless, Zvonarev et al achieved higher LHA yields by calcination in vacuum than by calcination in air. A reason for this observation was not given.…”