A series of Ln-doped KSrPO₄ (Ln = Ce³⁺, Eu³⁺, Eu²⁺, Pr³⁺) phosphors are prepared through a high-temperature solid-state method. The KSrPO₄ compound is confirmed to possess a β-K₂SO₄ structure with the Pnma group by Rietveld refinement, and the temperature-dependent lattice parameters are investigated with the powder X-ray diffraction results at different temperatures. Ce³⁺ and Eu³⁺ ions are introduced to probe the crystal field strength (CFS) and the lanthanide site symmetry by using VUV-UV-vis spectroscopy. The temperature-dependent luminescence properties of KSrPO₄: Ce³⁺/Eu²⁺ exhibit an excellent thermal stability of Ce³⁺/Eu²⁺ luminescence. Based on the VUV-UV-vis spectra of Ce³⁺ and Eu³⁺ doped KSrPO₄, the vacuum referred binding energy (VRBE) scheme is constructed to understand the redox properties of Eu, the 5d energy levels of Pr³⁺ and the thermal quenching characteristics of Ce³⁺ and Eu²⁺ luminescence.

The host structure and the synchrotron radiation VUV-UV luminescence properties of samples BaMg₂Si₂O₇ (BMSO):Ln (Ce³⁺, Eu²⁺) at different doping levels and different temperatures were investigated in detail. Three important aspects are studied to elucidate the luminescence properties of samples: (1) the vacuum referred binding energy (VRBE) scheme is constructed with the electron binding in the BMSO host bands and in the Ce³⁺ and Eu²⁺ impurity levels with the aim to explain the different thermal stabilities of Ce³⁺ and Eu²⁺ emissions; (2) the electron-vibrational interaction analysis on the narrow Eu²⁺ emission indicates a weak electron-phonon interaction in the current case; (3) by using three models (Inokuti-Hirayama, Yokota-Tanimoto, and Burshteǐn models) at different conditions, the energy transfer dynamics between Ce³⁺ and Eu²⁺ was analyzed. It reveals that the energy transfer from Ce³⁺ to Eu²⁺ via electric dipole-dipole (EDD) interaction is dominant while energy migration between Ce³⁺ is negligible. Finally, the X-ray excited luminescence spectra of samples BMSO:Ce³⁺/Eu²⁺ are collected to evaluate their possible scintillator applications.

A series of Ce³⁺-doped (Ca,Sr)₂Al₂SiO₇ phosphors with different Ce³⁺ and Ca²⁺/Sr²⁺ concentrations were prepared by a high temperature solid-state reaction technique. To get insight into the structure-luminescence relationship, the impact of incorporation of Sr²⁺ on structure of (Ca,Sr)₂Al₂SiO₇ was first investigated via Rietveld refinement of high quality X-ray diffraction (XRD) data, and then the VUV-UV excitation and UV-vis emission spectra of (Ca,Sr)₂Al₂SiO₇:Ce³⁺ were collected at low temperature. The results reveal that the crystal structure evolution of (Ca,Sr)₂Al₂SiO₇:Ce³⁺ has influences on band gaps and Ce³⁺ luminescence properties including 4f-5d_i (i = 1-5) transition energies, radiative lifetime, emission intensity, quantum efficiency, and thermal stability. Moreover, the influence of Sr²⁺ content on the energy of Eu³⁺-O^2- charge-transfer states (CTS) in (Ca,Sr)₂Al₂SiO₇:Eu³⁺ was studied in order to construct vacuum referred binding energy (VRBE) schemes with the aim to further understand the luminescence properties of (Ca,Sr)₂Al₂SiO₇:Ce³⁺. Finally, X-ray excited luminescence (XEL) spectra were measured to evaluate the possibility of (Ca,Sr)₂Al₂SiO₇:Ce³⁺ as a scintillation material.

In this work, we demonstrate a potential thermometric material after systematic studies on the concentration/temperature-dependent spectroscopic properties of Pr³⁺ excited multiplets and of the Pr³⁺-Ti⁴⁺ intervalence charge transfer (IVCT) state in (La_1-xPr_x)₂MgTiO₆. The experimental results indicate that the electron population efficiency between the involved Pr³⁺ 4f multiplets is directly governed by multi-phonon relaxation (MPR) and cross relaxation (CR), and the IVCT state provides an additional contribution to the ¹D₂ luminescence. A schematic energy level diagram is proposed to illustrate the electron population pathway in Pr³⁺ doped La₂MgTiO₆. The observations clarify that the dramatic thermal-quenching of ³P₀ luminescence is mainly induced by the electronic configuration crossover between the ³P₀ multiplet and the IVCT state. On the other hand, the ¹D₂ luminescence possesses an excellent thermal stability in a large temperature region. These temperature sensing features of the Pr³⁺ doped La₂MgTiO₆ material indicate its potential application in optical thermometric techniques.