## 3 Results and Discussion
[PERSON] _et al._ found that Eu\({}^{3+}\)-doped LiBaLaTeO\({}_{6}\), NaBaLaTeO\({}_{6}\), and LiBaBiTeO\({}_{6}\) show the dominant transition of \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{2}\) with a pure red luminescence color and Eu\({}^{3+}\)-doped NaCaBiTeO\({}_{6}\) presents the dominant reddish-orange emission from the transition of \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{1}\)[16]. Those results suggest that the different Eu\({}^{3+}\) ion transitions will happen. For one-step Eu-BZO powders, even the transition \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{1}\) dominated the emission as the heating temperature was equal to and higher than 1300 \({}^{\circ}\)C; however, they all presented the reddish-orange emission, as Figure 6a shows. For two-step Eu-BZO powders, the domination transition changed from \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{1}\) to \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{0}\) as the heating temperature increased from 1100 \({}^{\circ}\)C to 1400 \({}^{\circ}\)C; also, the emission changed from the reddish-orange color to orange, as Figure 6a-c show. Figure 5: Emission intensity of BaZrO\({}_{3}\):Eu\({}_{0.025}\) phosphors as a function of heating process and heating temperature. Solid-line: one-step Eu-BZO powders, dashed-line: two-step Eu-BZO powders. Figure 6: Photographs for the light emissions of heated Eu-BZO phosphors. (**a**) One-step Eu-BZO powder heated at 1300 \({}^{\circ}\)C and two-step Eu-BZO powders heated at (**b**) 1100 \({}^{\circ}\)C, (**c**) 1200 \({}^{\circ}\)C, and (**d**) 1400 \({}^{\circ}\)C, respectively. Phosphor materials are known for their use in radar screens and glow-in-the-dark toys, whereas fluorescent materials are common in cathode ray tubes (CRT) and plasma video display screens, sensors, and white LEDs. The activators have the effect of prolonging the emission time (afterglow) and some other materials, such as nickel, can be used to quench the emitting intensity and shorten the decay time of the phosphor emission characteristics. The intensity decay of the PL process can be expressed in the following functional form:  
\[I_{\text{em}}\;=\;I_{0}\exp\left(-t/\tau\right) \tag{1}\]  
where the lifetime \(\tau\) refers to the time required for the intensity to drop to \(I_{0}/\text{e}\), \(I_{0}\) is the initial intensity, and \(I_{\text{em}}\) is the intensity at time \(t\). [PERSON] _et al._ also found that Eu\({}^{3+}\)-doped LiBaLaTeO\({}_{6}\), NaBaLaTeO\({}_{6}\), and LiBaBiTeO\({}_{6}\) show a fast decay and Eu\({}^{3+}\)-doped NaCaBiTeO\({}_{6}\) presents a longer luminescence lifetime [16]. As Figure 7 shows, the one-step Eu-BZO phosphors exhibited decay lifetimes extending from 2.52 ms to 3.98 ms and the two-step Eu-BZO phosphors exhibited decay lifetimes extending from 3.78 ms to 6.02 ms. As we know in Zn\({}_{2}\)SiO\({}_{4}\)-MnO\({}_{2}\) phosphors, if too much MnO\({}_{2}\) dopant is added, a concentration quenching effect occurs, with resulting degeneration of the emission intensity and decay time [20; 21]. [PERSON] _et al._ also found that as the Mn\({}^{+2}\) dopant concentration and the heating temperature increase, the chance for MnO\({}_{2}\) to substitute for ZnO increases and the concentration of Mn\({}^{+2}\) ions increases. Energy transfer between Mn\({}^{+2}\) and Mn\({}^{+2}\) ions is expected to happen, which will take the excitation energy too far from the absorption location [21]. Equation (1) is most commonly used to describe the lifetime of phosphor materials with exponential decay and any one of the decay constant, mean lifetime, or half-life is sufficient to characterize the decay. It is known that the presence of impurities or crystal defects in semiconductors determines the lifetime of carriers, because a modified electronic structure within the crystal will give rise to defect levels, or energy levels that do not lie near the edge of the band gap.