Structural and electronic properties of β-NaYF4 and β-NaYF4:Ce3+

Abstract

In this work, the density functional theory approach with linear combination of atomic orbitals (LCAO) as implemented in the CRYSTAL17 computer code is applied to hexagonal β-NaYF 4 , located in three possible space groups of this compound: P6, P6 3 /m and P6 2 m. First, the disordered crystalline structure of NaYF 4 was modelled in a large supercell containing 108 atoms. In order to obtain better agreement with the experimental data, we used several different exchange-correlation functionals. Basic properties, such as lattice constant, band gap and total energies were calculated and compared for all three space groups and three exchange-correlation functionals-HSE06, PWGGA and PWGGAþ13%HF. It was found that for all three functionals, the minimum of total energy corresponds to P6 space group. Secondly, in order to study the effects associated with the Ce 3þ impurity and the F center (radiation defect), the P6 β-NaYF 4 structure with the F center and Ce 3þ or with both was carefully modelled. Taking into account that fluorine atoms have different nearest neighbours, several types of fluorine vacancies were simulated and an appropriate formation energies were determined. Finally, the effects of Ce 3þ ion substitution of Y ions in different positions as well as formation of Ce 3þ , the F center defect pairs were also studied and an appropriate incorporation energies were calculated.

Synthesis and characterization of fluorinated polyimide doped with NaYF4 nanocrystals for optical waveguide applications

“…The resulting NCs exhibited colloidal stability in organic solvent for weeks without visible aggregation or settling. 25,27–29…”

“…Nanocrystals (NCs) were prepared using a procedure described in previous studies, with some modifications. [24][25][26][27][28][29] All experiments were conducted under an argon atmosphere using standard Schlenk techniques. In a typical synthesis, fixed amounts of Er 3 O 3 (14.34 mg, 0.0375 mmol) or Yb 2 O 3 (147.78 mg, 0.375 mmol) and Y 2 O 3 (330.25 mg, 1.4625 mmol) were mixed with 50% aqueous trifluoroacetic acid (15 mL) and heated to 80°C to obtain the lanthanide trifluoroacetate precursors.…”

“…The resulting NCs exhibited colloidal stability in organic solvent for weeks without visible aggregation or settling. 25,[27][28][29] The morphology and the particle size distribution of the nanoparticles have been examined by transmission electron microscopy. Figure 2 110), ( 101), ( 201), (300), (211) peaks of β-NaYF 4 phase structure.…”

ENHANCING PHOTOMETRIC PERFORMANCE OF YAG:CeCERAMICS: INVESTIGATING THE ROLE OF ANNEALING IN RADIATION-ASSISTED SYNTHESIS

“…Phosphor materials play a crucial role in various modern technologies, particularly in the fields of lighting and display systems. These materials possess the unique ability to convert energy from one form into another, most commonly transforming ultraviolet (UV) or high-energy visible light into lower-energy visible light [1][2][3][4] Among the numerous phosphor materials available, Ce 3+ -doped luminescent phosphors have emerged as a promising candidate for a range of applications [5][6][7][8][9][10]. In particular, cerium-doped yttrium aluminum garnet (YAG:Ce) phosphor ceramics are innovative materials that evolve from the base compound of YAG, doped with cerium (Ce) ions.…”