On the kinetics of thermal oxidation of the thermographic phosphor BaMgAL 10 O 17 :Eu

Abstract

Decreased photoluminescence of the phosphor BaMgAL 10 O 17 :Eu due to oxidation of the europium dopant at high temperatures has been a subject of study for many years in relation to its use in lighting applications. However, understanding of the underlying effects that cause this reduction in photoluminescence remains incomplete and some of the mechanisms proposed in the literature are contradictory. Recent use of this phosphor as a thermal history sensor has extended the range of exposure conditions normally investigated in lighting applications to higher temperatures and multiple exposure times. The kinetics of the process were investigated by means of spectroscopy and material characterisation techniques. It was found that changes in the luminescence are the result of two simultaneous processes: the oxidation of Eu 2+ ions (through a process of diffusion) and a phase transition. The level of degradation of the phosphor is suggested to follow the Kolmogorov-JohnsonMehl-Avrami (KJMA) model above 900 °C and thus can be predicted with knowledge of the exposure time and temperature. This is useful in applications of the phosphor as a temperature sensor.

Investigation of the tin-doped phosphor (Sr,Mg)3(PO4)2:Sn2+ for fluid temperature measurements

“…Exposures of the phosphor in air for 30 mins at 630 • C, and 730 • C, led to a reduction in room temperature brightness of 10% and 57%, respectively [12]. The thermal stability is similar in terms of the temperature/heat treatment duration space to that of BAM:Eu 2+ [17,18]. Note that this is not a concern for short residence times of the particles at high temperatures when used in flows.…”

Investigation of BAM:Eu2+ particles as a tracer for temperature imaging in flames

“…Previously, it was shown that, for BAM : Eu 2+ particles, the temperature calibration remained unchanged before and after combustion in a vessel [9]. This corresponded to an exposure of 0.5 s between 1400 and 2000 K. In a study of much longer exposures (20 min) at 1470 K, only a subtle change in the room temperature emission spectrum was observed [10], translating to an ∼80 K calibration error. Therefore, it is reasonable to assume that short exposure to high temperatures does not alter the luminescence emission spectrum.…”

“…However, in Refs [10,11], exposures of several minutes at these temperatures caused the luminescence emission intensity to decrease by orders of magnitude, a phenomenon referred to as thermal degradation. This second phenomenon has not yet been investigated for short exposure times relevant to reactive flows, though it would be problematic since it would compromise the measurement precision.…”

Eu2+luminescence in CaYGaO4olivine: a new efficient red phosphor for warm illumination

“…Among fluorides, oxides, sulfides, and chlorides, which are usually explored as phosphor hosts, oxides are regarded as the most promising candidates because of their excellent physical/chemical durability and mild preparation conditions at ambient pressure. 26,27 It is known that the Eu 2+ :4f 6 5d 1 energy is governed by the nephelauxetic effect and crystal field splitting effect. The former follows the F − < O 2− < Cl − < N 3− < S 2− nephelauxetic sequence.…”