Design, Preparation, and Characterization of a Novel Red Long-Persistent Perovskite Phosphor: Ca₃Ti₂O₇:Pr³⁺

Abstract

Currently, the development of efficient red-emitting persistent phosphor is still an ongoing challenge. Herein, a novel red-emitting LPL phosphor Ca3Ti2O7:Pr(3+) is successfully prepared by a high-temperature solid-state method. XRD Rietveld refinement analyses demonstrate the high phase purity of the sample which crystallizes in an orthorhombic Ccm21 space group with lattice parameters of a = 5.7702(5) Å, b = 19.4829(7) Å, and c = 5.1214(2) Å. Electronic structure of the host matrix is analyzed by the first-principle calculation using CASTEP code. The calculation results show that Ca3Ti2O7 has a direct band gap with CB and VB mainly composed of the Ti-3d and O-2p states, respectively. On the basis of the DR spectrum, the band gap is determined to be 3.6 eV. It is demonstrated that the 612 nm red-emitting persistent luminescence of Ca3Ti2O7:Pr(3+) can be either activated by Ti(4+)-O(2-) → Ti(3+)-O(-) host absorption and Pr(3+)-O-Ti(4+) → Pr(4+)-O-Ti(3+) IVCT in the UV region, or Pr(3+):(3)H4 → (3)PJ transition in the blue region. The red afterglow can last for ∼ 5 min observed by the naked eyes in the dark after ceasing the irradiation source. On the basis of the TL analyses, the trap is found exponentially distributed in the host with the depth of 0.69-0.92 eV. Finally, a possible LPL mechanism for Ca3Ti2O7:Pr(3+) is proposed.

Trap distribution and photo‐stimulated luminescence in LaSrAl3O7:Eu2+ long‐lasting phosphors for optical data storage

“…According to the Kubelka‐Munk function, the calculated band gap is 4.6 eV (Figure B). The computed energy gap of LaSrAl 3 O 7 indicates that the material is a good luminescent host for accommodating both the ground and excited states of luminescent ions within the wide band gap . Using the XPS method, the chemical states of various elements are confirmed.…”

“…It is clearly that the top of the VB is composed chiefly of O p states with a dispersion of ~ 5.9 eV, whereas the bottom of the CB consists mainly of La p and d , Sr d and Al p states. It is well acknowledged that the DFT calculation always underestimates the energy band gap of crystals due to the inherent shortcoming of DFT method . The UV‐Vis‐NIR diffuse‐reflectance (DR) spectrum is shown in Figure .…”

“…An initial rising method was further applied to TL curves to reveal the shallowest occupied trap depth ( E ) at each T exc , as presented in Figure . This method assumes that the concentration of trapped electrons on the low‐temperature side of a TL glow curve remains relatively constant; thus, the TL intensity ( I (T)) can be approximately expressed as follows:where C is the constant including the frequency factor s , and k is the Boltzmann constant. By plotting the TL curves as ln( I ) vs 1000/T, the shallowest trap depth E can be determined by the slope of a fitted straight section at the low‐temperature side.…”

A Photostimulated BaSi2O5:Eu2+,Nd3+ Phosphor‐in‐Glass for Erasable‐Rewritable Optical Storage Medium

“…Upon Eu 2+ or Nd 3+ doping, new‐type traps showing much higher TL intensity are created. Though these traps still cannot be specifically designated at present, we can give some speculations: the positive defect and the barium vacancy maybe produced via to compensate the nonequivalent substitution of Ba 2+ by Nd 3+ …”

Toward tunable and bright deep‐red persistent luminescence of Cr3+ in garnets

“…It is also worth noting that all of the Cr 3+ singly doped garnet ceramic samples exhibit PersL behaviors even at 20 K after ceasing blue light excitation as shown in Figure (B) (take the GSG G :Cr sample as an example). The reciprocal PersL intensity of the GSG G :Cr sample vs time after ceasing 460 nm charging presents a linear behavior which indicates that there is a strong athermal tunneling process in this material . As the schematic illustration of the Cr 3+ energy levels in the GSG G :Cr sample shown in Figure (C), blue light (460 nm) charging can only facilitate the 4 T 1 ( 4 F) energy level of Cr 3+ which has a large energy gap below the bottom of CB so that the classical electron trapping‐detrapping channel through CB cannot occur.…”