Optimizing the Structure and Optical Properties of Lanthanum Aluminate Perovskite through Nb5+ Doping

This work involves the introduction of niobium oxide into lanthanum aluminate (LaAlO3) via a conventional solid-state reaction technique to yield LaAlO3:Nb (LaNbxAl1-xO3+δ) samples with Nb5+ doping levels ranging from 0.00 to 0.25 mol%. This study presents a comprehensive investigation of the effects of niobium doping on the phase evolution, defect control, and reflectance of LaNbxAl1-xO3+δ powder. Powder X-ray diffraction (XRD) analysis confirms the perovskite structure in all powders, and XRD and transmission electron microscopy (TEM) reveal successful doping of Nb5+ into LaNbxAl1-xO3+δ. The surface morphology was analyzed by scanning electron microscopy (SEM), and the results show that increasing the doping concentration of niobium leads to fewer microstructural defects. Oxygen vacancy defects in different compositions are analyzed at 300 K, and as the doping level increases, a clear trend of defect reduction is observed. Notably, LaNbxAl1-xO3+δ with 0.15 mol% Nb5+ exhibits excellent reflectance properties, with a maximum infrared reflectance of 99.7%. This study shows that LaNbxAl1-xO3+δ powder materials have wide application potential in the field of high reflectivity coating materials due to their extremely low microstructural defects and oxygen vacancy defects.

Investigation on the upconversion luminescence and ratiometric thermal sensing of SrWO4:Yb3+/RE3+ (RE = Ho/Er) phosphors

SrWO₄ phosphors doped with Ho³⁺(Er³⁺)/Yb³⁺ are successfully prepared by a high temperature solid-state reaction method. The upconversion (UC) luminescence properties of all the samples have been investigated under 980 nm excitation. Strong green emissions are obtained in the SrWO₄:Yb³⁺/Ho³⁺ and SrWO₄:Yb³⁺/Er³⁺ samples with the naked eyes. In a temperature range going from 303 K to 573 K, the UC emission spectra of the phosphors have been measured. Then the temperature sensing properties also have been discussed via fluorescence intensity ratio (FIR) technology. For the SrWO₄:Yb³⁺/Ho³⁺ phosphor, the FIR technologies based on thermal coupling levels (TCLs)(⁵F₄,⁵F₅) and non-thermal coupling levels (non-TCLs)(⁵S₂, ⁵F₄/⁵F₅) are used for investigating the sensitivity. The results show that the maximum absolute sensitivity reaches 0.0158 K⁻¹ with non-TCLs. As for Yb³⁺/Er³⁺ codoped SrWO₄ phosphor, the maximum absolute sensitivity reaches 0.013 K⁻¹ with TCLs (²H_11/2,⁴S_5/2) at a temperature of 513 K. These significant results demonstrate that the SrWO₄:Ho³⁺(Er³⁺)/Yb³⁺ phosphors are robust for optical temperature sensors.

SrWO₄ phosphors doped with Ho³⁺(Er³⁺)/Yb³⁺ are successfully prepared by a high temperature solid-state reaction method.

Highly efficient upconversion of Er3+ in Yb3+ codoped non-cytotoxic strontium lanthanum aluminate phosphor for low temperature sensors

Er³⁺ and Er³⁺/Yb³⁺ melilite-based SrLaAl₃O₇ (SLA) phosphors were synthesized by a facile Pechine method. The differences in emission intensities of ⁴I_13/2 → ⁴I_15/2 transition in NIR region when excited with Ar⁺ and 980 nm lasers were explained in terms of energy transfer mechanisms. Temperature and power dependence of upconversion bands in the visible region centered at 528, 548 and 660 nm pertaining to ²H_11/2, ⁴S_3/2 and ⁴F_9/2 → ⁴I_15/2 transitions were investigated. Fluorescence intensity ratio (FIR) technique was used to explore temperature sensing behaviour of the thermally coupled levels ²H_11/2/⁴S_3/2 of Er³⁺ ions in the phosphors within the temperature range 14–300 K and the results were extrapolated up to 600 K. Anomalous intensity trend observed in Er³⁺ doped SLA phosphor was discussed using energy level structure. Cytotoxicity of phosphors has been evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in Bluegill sunfish cells (BF-2). The non-cytotoxic nature and high sensitivity of the present phosphors pay a way for their use in vitro studies and provide potential interest as a thermo graphic phosphor at the contact of biological products.

Improving Optical Temperature Sensing Performance of Er3+ Doped Y2O3 Microtubes via Co-doping and Controlling Excitation Power

This work presents a new method to effectively improve the optical temperature behavior of Er³⁺ doped Y₂O₃ microtubes by co-doping of Tm³⁺ or Ho³⁺ ion and controlling excitation power. The influence of Tm³⁺ or Ho³⁺ ion on optical temperature behavior of Y₂O₃:Er³⁺ microtubes is investigated by analyzing the temperature and excitation power dependent emission spectra, thermal quenching ratios, fluorescence intensity ratios, and sensitivity. It is found that the thermal quenching of Y₂O₃:Er³⁺ microtubes is inhibited by co-doping with Tm³⁺ or Ho³⁺ ion, moreover the maximum sensitivity value based on the thermal coupled ⁴S_3/2/²H_11/2 levels is enhanced greatly and shifts to the high temperature range, while the maximum sensitivity based on ⁴F_9/2(1)/⁴F_9/2(2) levels shifts to the low temperature range and greatly increases. The sensitivity values are dependent on the excitation power, and reach two maximum values of 0.0529/K at 24 K and 0.0057/K at 457 K for the Y₂O₃:1%Er³⁺, 0.5%Ho³⁺ at 121 mW/mm² excitation power, which makes optical temperature measurement in wide temperature range possible. The mechanism of changing the sensitivity upon different excitation densities is discussed.

Luminescence, energy transfer and optical thermometry of a novel narrow red emitting phosphor: Cs2WO2F4:Mn4+

Novel thermometry based on two coupled vibrational sidebands of Mn⁴⁺.

Yb3+-Concentration dependent upconversion luminescence and temperature sensing behavior in Yb3+/Er3+ codoped Gd2MoO6 nanocrystals prepared by a facile citric-assisted sol–gel method

Er³⁺/Yb³⁺-Codoped Gd₂MoO₆ upconversion nanocrystals with high sensor sensitivity and wide operation range were demonstrated for non-contact optical thermometry.

Tunable emissions via the white region from Sr2Gd8(SiO4)6O2:RE3+ (RE3+: Dy3+, Tm3+, Eu3+) phosphors

Sr₂Gd₈(SiO₄)₆O₂ is an excellent host lattice for tunable emissions via the white-light region when co-doped with suitable trivalent rare-earth ions.

Stark sublevels of Er3+–Yb3+ codoped Gd2(WO4)3 phosphor for enhancing the sensitivity of a luminescent thermometer

Using the FIR technique, the temperature sensing behavior is investigated based on five pairs of thermal coupling levels (²H_11/2/⁴S_3/2(2), ²H_11/2/⁴S_3/2, ²H_11/2/⁴S_3/2(1), ⁴S_3/2(2)/⁴S_3/2(1) and ⁴F_9/2(2)/⁴F_9/2(1)).

Investigation into optical heating and applicability of the thermal sensor bifunctional properties of Yb3+ sensitized Tm3+ doped Y2O3, YAG and LaAlO3 phosphors

Bifunctional properties of Yb³⁺ sensitized Tm³⁺ doped Y₂O₃, YAG and LaAlO₃ phosphors were investigated according to experimental and theoretical calculations.