## 1 Introduction
In Mg\({}^{2+}\) and Pr\({}^{3+}\) co-doped LiNbO\({}_{3}\) perovskite single crystals, [PERSON] et al. found persistent bright-red LPL generated by a wide range of near-UV excitation; they then proposed a charge relaxation mechanism based on the transition between the intermediate defect states [12]. NaNbO\({}_{3}\) doped with Pr\({}^{3+}\) ions could be excited in the near-UV region of approximately 350 nm, resulting in a bright single red emission at room temperature, which was attributed to the transition between the excited state, \({}^{1}\)D\({}_{2}\), and the ground state, \({}^{3}\)H\({}_{4}\), of the Pr\({}^{3+}\) ions [13]. In summary, the electronic transitions corresponding to the red and near-infrared emissions of Pr\({}^{3+}\) mainly include \({}^{1}\)D\({}_{2}\)\(\rightarrow\)\({}^{3}\)H\({}_{4}\) (610 nm), \({}^{1}\)D\({}_{2}\)\(\rightarrow\)\({}^{3}\)H\({}_{5}\) (720 nm), \({}^{1}\)D\({}_{2}\)\(\rightarrow\)\({}^{3}\)H\({}_{6}\) (900 nm), and \({}^{1}\)D\({}_{2}\)\(\rightarrow\)\({}^{3}\)F\({}_{3,4}\) (1080 nm). Also, Pr\({}^{3+}\)-doped luminescent materials had stable red LPL properties. Pr\({}^{3+}\), as the luminescent center of red LPL, had broad application prospects in several fields, such as scintillators, emergency lighting, and biomedicine, and has been widely studied in the past [14; 15]. In addition, [PERSON] et al. discovered that the mechanical luminescence in NaNbO\({}_{3}\):Pr\({}^{3+}\) and Er\({}^{3+}\) was a physical phenomenon, whereby the material can emit light visible to the naked eye under the influence of stress, friction, scratch, fracture, and ultrasonic oscillation; they determined that it originates from the triple coupling of the piezoelectricity, trap energy level, and Pr\({}^{3+}\) center [16]. [PERSON] et al. reported a well-known multifunctional piezoelectric material that exhibited both piezoelectricity and efficient piezo-luminescence. In LiNbO\({}_{3}\):Pr\({}^{3+}\), Pr was substituted into the Li sites [17]. The prepared mechanical luminescent particles were embedded into polymers or other films into composite materials to achieve waterproofing and flexibility, and they could also provide multidimensional information that could be observed. The emergence of this multimode luminescent material enables Pr\({}^{3+}\)-doped luminescent materials to offer unique insights for designing highly integrated stimuli-responsive smart devices and for applications in anti-counterfeiting, wireless detection, nondestructive analysis, stress sensing, damage diagnosis, and other fields. During the past two decades, there were series of significant advances in the field of luminescent materials, including the discovery of new phosphors, the development of novel characterization methods, and an in-depth understanding of the mechanism of luminescence [18; 19; 20; 21; 22]. Among these, a series of well-known visible and infrared long persistent luminescent materials was discovered and rapidly applied in night vision monitoring, medical diagnosis, and optical information storage [23; 24; 25; 26; 27]. Additionally, NaNbO\({}_{3}\) and LiNbO\({}_{3}\) were promising optoelectronic lead-free insulating piezoelectric substrates, which were suitable for various applications, such as modulators, storage devices, sensors, and actuators [28; 29]. Therefore, in this study, we prepared and analyzed a series of Pr\({}^{3+}\)-doped niobate phosphor red LPL materials, combining the excellent properties of NaNbO\({}_{3}\) and LiNbO\({}_{3}\) matrices with Pr\({}^{3+}\) luminescent centers to exhibit red LPL and ML properties. Through this study, we can further elucidate the structural properties, clarify the luminescence mechanism, and improve the luminescence performance of these materials. Owing to their red LPL and ML properties, Pr\({}^{3+}\)-doped niobate phosphors can be employed in fields, such as display technologies, stress sensing, structural damage detection, image anti-counterfeiting of luminescent inks, and other complex applications.