Kinetic Study of the Thermal Quenching of the Ultraviolet Emission in Zn₂GeO₄ Microrods

Abstract

Zn2GeO4 microrods obtained by thermal evaporation of a compacted powder mixture of ZnO and Ge exhibit quite intense UV luminescence at low temperatures. Herein, the luminescence properties of Zn2GeO4 microrods are studied for 2:1 and 1:1 ZnO:Ge ratio in the precursor mixture. In both cases, Zn2GeO4 microrods of high crystal quality produce a 355 nm emission under aforementioned bandgap excitation conditions at low temperatures. However, this emission vanishes at room temperature (RT) in the 1:1 samples while it is kept in the 2:1 ones. Herein this work, the thermal quenching of the UV luminescence is studied by means of steady and time‐resolved photoluminescence techniques from 4 K up to RT for both Zn2GeO4 microrods. The analysis of the results leads us to conclude that although the luminescence mechanisms are the same in both cases, a higher decay rate is observed in the 1:1 in both intensity and lifetime, which explain the observed thermal quenching at RT.

Trap engineering through chemical doping for ultralong X-ray persistent luminescence and anti-thermal quenching in Zn2GeO4

“…The activation energy of the TQ process of Zn 2 GeO 4 emissions is 68 meV and this can be attributed to non-radiative relaxations when charge carriers have enough energy for crossover due to thermal activation. 56,61 In contrast, for the 0.01Pr sample, the PL intensity remained constant up to 180 K and then increased gradually, showing a weak NTQ effect. After T > 220 K, the PL intensity decreased abruptly due to PTQ processes.…”

“…The PL intensity remained almost constant for T < 120 K and above 120 K, and a strong PTQ of the Zn 2 GeO 4 emission band was observed under below-bandgap NUV excitations. The PTQ process can be modeled by using the expression with a single non-radiative process as below: 61,62 I T = I 0 /(1 + A exp(− E 1 / k B T ))…”

“…However, the TQ processes like thermal ionization and crossover dominate at higher temperatures due to a significant increase in non-radiative vibrational relaxations. 39,61 The activation energy of 0.36 eV for the 0.01Pr sample suggested good thermal stability of the green PL band for the 0.01Pr sample (Fig. 9d) in the temperature range of 358-398 K.…”

Local Structure and Speciation-Driven UO22+ → Sm3+ Energy Transfer for Enhanced Luminescence in Li2B4O7

“…The decay of Sm 3+ emissions can be fitted by exponential functions obtained from modified Arrhenius expression for a single barrier thermal quenching model: , τ T = τ 0 / ( A + B exp false( − E a / k B T false) ) where τ 0 and τ T denote the lifetimes at initial temperature ( T 0 ) and at temperature ( T ), E a is the activation energy for thermal quenching, A , B , and C are constants, and k B is the Boltzmann constant, respectively. An activation energy of 4027 ± 792 cm –1 was calculated from the exponential fit (τ T /τ 0 = 1/[0.98 + 1.05exp(−4027/(0.695 T ))]) shown in Figure f.…”