## 1 Introduction
[PERSON] and [PERSON] adopted a standard solid-state reaction method to investigate the properties of Eu-doped YPVO\({}_{4}\), Y\({}_{2}\)O\({}_{3}\), and YLaVO\({}_{4}\) phosphors [14]. They used a 254 nm wavelength to excite the photoluminescence emission spectra of YPVO\({}_{4}\): Eu\({}^{3+}\)(0.5%) and Y\({}_{2}\)O\({}_{3}\):Eu\({}^{3+}\)(0.5%), and Y(PV)O\({}_{4}\):Eu\({}^{3+}\) displayed photoluminescence (PL) emissions at 365, 540, 561, 594, and 611 nm, and Y\({}_{2}\)O\({}_{3}\):Eu\({}^{3+}\) displayed PL emissions at 536, 583, 589, 594, 600, 615, and 632 nm, respectively. They used a 450 nm wavelength to excite the Y\({}_{0.5}\)LaVO\({}_{4}\):Eu (0.5%) phosphor and it generated a strong and broad emission in the UV region of 240 to 300 nm [14]. [PERSON] _et al._ found that Eu\({}^{2+}\)-doped \(\alpha\)-salion phosphor exhibited wide absorption in ultraviolet (UV) and visible range, and a high broad emission band peaking at from 570 to 582 nm [15]. [PERSON] _et al._ investigated the Eu\({}^{3+}\)-doped double-perovskite LiBaLa[TeO\({}_{6}\)], NaBaLa[TeO\({}_{6}\)], and LiBaBi[TeO\({}_{6}\)] compositions as phosphors. They found that those double-perovskite powders show the dominated electric dipole transition \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{2}\) with a pure red luminescence color and a fast decay. They also found that Eu\({}^{3+}\)-doped NaCaBi[TeO\({}_{6}\)] presents the dominant reddish-orange emission from the magnetic dipole transition \({}^{5}\)D\({}_{0}\)\(\rightarrow\)\({}^{7}\)F\({}_{1}\) and a longer luminescence lifetime [16]. In the past, [PERSON] _et al._ synthesized Eu-doped BaZrO\({}_{3}\) fine particles with high crystallinity by using hydrothermal reactions and they also investigated the effect of size and shape on the fluorescence properties of Eu-doped BaZrO\({}_{3}\) for its use as a phosphor [17]. The Eu\({}^{3+}\)-doped orthorhombic BaZrO\({}_{3}\) (Eu-BZO) powders could be synthesized by the traditional one-step high temperature solid-state reaction method [11]. In the past, we had found that different heating and fabrication processes will have a large effect on the properties of prepared ceramics. For example, we prepared the 0.95 (Na\({}_{0.5}\)Bi\({}_{0.5}\))TiO\({}_{3}\)-0.05 BaTiO\({}_{3}\) ceramics with different heating processes and we found that the heating process had a large effect on their crystalline and electrical properties [18]. Nevertheless, no research has focused on the effect of different heating processes on the luminescent properties of BaZrO\({}_{3}\) powders. Thus, in this study, we investigated two different heating processes to synthesize the Eu-BZO powders by the traditional solid-state reaction method. The first was the one-step solid-state reaction method, where the Eu-BZO powders were directly heated to 1100 \({}^{\circ}\)C-1400 \({}^{\circ}\)C. The second was the two-stepsolid-state reaction method, where the Eu-BZO powders were pre-heated at 800 \({}^{\circ}\)C and then heated to 1100 \({}^{\circ}\)C-1400 \({}^{\circ}\)C after cooling. After the different heating processes, the optical properties of BaZrO\({}_{3}\) powders as a function of different heating temperatures were presented. The heated BaZrO\({}_{3}\) powders showed two strong orange emission bands peaking at the wavelengths of 574 and 596 nm and two weak emission bands peaking at around 620 and 650 nm under the excitation optimum optical wavelength of 271 nm. We found that the heating process would have a large effect on the properties of the emission spectrum of Eu-BZO powders and we would investigate the luminescent properties of BaZrO\({}_{3}\) powders under different heating processes in detail.