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Öğe Eco-friendly synthesis of Eu3+, Sm3+, and Dy3+-doped monticellite-based ceramic powders: effects of rare-earth dopants and synthesis temperature(Springer, 2023) Köroğlu, Levent; Karacaoğlu, Erkul; Demir, Burak; Ağil, Aslı Asiye; Ayas, ErhanEco-friendly luminescent monticellite-based ceramic powders were synthesized from boron derivative waste at low temperatures. It aimed to investigate the effects of rare-earth dopants and synthesis temperature on phase evolution, photoluminescence properties, and microstructural development of Eu3+, Sm3+, and Dy3+-doped powders. The powders synthesized at 800 °C and 900 °C include the same major phases: monticellite, akermanite, and calcium magnesium borate. No rare-earth oxide clusters are observed during their microstructural analysis. However, powders produced at 800 °C give stronger emission lines than 900 °C. Eu3+-doped powders exhibited characteristic emission at 619 nm originating from the 5D0 → 7F2 transition under excitation at 248 nm, assuring CIE color coordinates of standard red light. A strong emission in the orange-red region (610 nm) is assigned to the 4G5/2 → 6H7/2 transition of Sm3+ upon excitation at 408 nm. Moreover, Dy3+-doped powders demonstrate two major emission lines at 489 nm (blue) and 583 nm (yellow) attributed to typical 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions under 392 nm, providing the color coordinates of CIE (Commission International de I’Eclairage) close to white light. Therefore, RE3+-doped monticellite-based ceramic powders, produced from boron derivative waste in an eco-friendly way, carry the potential to be used as luminescent materials for lighting, display, and bioimaging applications. Graphical abstract: [Figure not available: see fulltext.].Öğe Effect of Gd-codoping on photoluminescence properties of Eu-doped natural fluorapatite(Elsevier GmbH, 2023) Demir, Burak; Karacaoğlu, Erkul; Agil, Asli Asiye; Koroglu, Levent; Ayas, ErhanThis study investigated the photoluminescence properties of Eu, Gd, and Eu-Gd co-doped natural fluorapatite (FAP) particles. Ca10(PO4)6F2:EuxGd0.2−x powders were synthesized by the solid-state powder synthesis method at 1150 ⁰C. X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-Ray Spectroscopy, and Photoluminescence Spectroscopy (PL) were used to characterize the structural, morphological, chemical, and optical properties, respectively. XRD and FTIR analysis demonstrated the presence of mainly FAP while CaO and larnite as minor phases. Approximately 1–2 µm equiaxed FAP particles were seen in SEM microstructure images. Regardless of Gd3+, in the presence of Eu3+, under 253 nm excitation, the FAP samples showed characteristic emission bands of Eu3+ at 600 nm and 625 nm originating from 5D0→7F1 and 5D0→7F2 transitions, respectively. In addition, a noticeable increase was observed in the emission intensity of Eu3+ with the addition of Gd3+. On the other hand, the Gd-doped FAP sample showed an emission band at 320 nm originating from the Gd3+ 6P7/2→8S7/2 transition under excitation at 205 nm. As a result, the emissions of Eu-FAPs were improved with the Gd-codoping, and materials with high color purity and excellent chromaticity coordinate characteristics were obtained.Öğe Effects of doping content and crystallite size on luminescence properties of Eu3+ doped fluorapatites obtained from natural waste(Elsevier Ltd., 2021) Demir, Burak; Derince, Dilara; Dayioğu, Tolga; Köroğlu, Levent; Karacaoğlu, Erkul; Uz, Veli; Ayas, ErhanIn this study, Eu3+ doped natural fluorapatites [Ca10(PO4)6F2:xEu3+ (x = 0.1, 0.3 and 0.5)] were produced from a natural waste by solid-state powder synthesis, conventional sintering, and spark plasma sintering techniques. The effects of doping content and crystallite size on luminescence properties of fluorapatite were investigated by XRD, SEM, and PL analysis. The obtained results showed that luminescence emission's intensity significantly increased with doping content, but no effect was observed on the density and crystallite size. For the samples produced with different methods, emission intensity was the lowest for sintered samples by SPS (1150 °C, 10 min, 50 MPa) with the smallest crystalline size. In contrast, emission intensity was found much higher for synthesized powders with the largest crystallite size. Furthermore, upon excitation under UV radiation, the Eu doped fluorapatites demonstrated the characteristic 5D0–7F2 and 5D0–7F4 emission lines of Eu3+ at 618 nm and 704 nm (red region) with an ultrahigh intensity that has been firstly observed in the literature. Therefore, Eu doped fluorapatites, quickly produced from a natural waste in an eco-friendly and cost-effective way, carry a potential to be used in biological applications and lightning applications.Öğe Synthesis and characterization of luminescent er3+-doped natural fluorapatite(Electrochemical Soc Inc., 2022) Demir, Burak; Karacaoğlu, Erkul; Ayas, ErhanCa-10(PO4)(6)F-2:xEr(3+) (x = 0.1, 0.3 and 0.5) was synthesized using solid-state powder process (1150 degrees C, 1h), conventional sintering (1150 degrees C, 1h), and spark plasma sintering (SPS) techniques (1150 degrees C, 10 min, and 50 MPa). XRD analysis revealed that all samples are generally composed of fluorapatite (FAP) containing quartz as a minor phase, and the presence of Er2O3 peaks is becoming more evident as Er-doped increases. In the SEM microstructure images, non-diffused Er2O3 particles also increase with doping in powder and pellet samples. However, the PL analysis showed that the luminescence intensity did not increase proportionally with the doping content caused by the concentration quenching effect. FAP samples doped with 0.3 mol Er have higher luminescence intensity than 0.1 and 0.5 mol Er-doped samples. In addition, powder samples have the highest luminescence intensity due to increased luminescence intensity with increasing crystallite size. The characteristic H-2(11/2) to I-4(15/2) emission bands of Er3+ at similar to 530 nm are seen in all samples. The maximum average lifetime was obtained in 125 mu s in the powder sample with 0.3 mol Er. CIE color coordinates demonstrate the standard green color under similar to < i 275 nm excitation; eventually, these phosphors can be utilized as green phosphors for optical applications.
