Low phonon energy BaCl₂ nanocrystals in Nd³⁺-doped fluorozirconate glasses and their influence on the photoluminescence properties

Abstract

Nd3+-doped fluorozirconate glasses, which were additionally doped with chlorine ions, were investigated for their photoluminescence (PL) properties. Upon heat treatment of the asmade glass, hexagonal phase BaCl 2 nanocrystals are formed within the material, which undergo a phase transformation to orthorhombic BaCl2 upon annealing at a higher temperature. The glasses with hexagonal phase BaCl2 nanocrystals show an enhanced Nd3+PL in the visible spectral range. Time-resolved spectroscopy on the 4G5/2 / 2G7/2 4I9/2 transition shows that the existence of hexagonal BaCl2 nanocrystals results in a significantly longer decay time. The temperature dependence of the lifetime yielded that the enhanced PL is due to a reduced multi-phonon relaxation rate

Judd‐Ofelt Calculations for Nd3+‐Doped Fluorozirconate‐Based Glasses and Glass Ceramics

“…As shown previously [6,7], a uniform growth of BaCl 2 nanocrystals inside such glasses can be induced by thermal treatment as soon as additional chloride is introduced at the expense of fluoride. Since BaCl 2 has a maximum phonon energy on the order of 200 cm −1 [3,8], MPR is rendered even less probable and, thus, rare-earth ions tend to favor radiative decays [6,7,9].…”

“…Since BaCl 2 has a maximum phonon energy on the order of 200 cm −1 [3,8], MPR is rendered even less probable and, thus, rare-earth ions tend to favor radiative decays [6,7,9].…”

Highly Efficient and Broadband Upconversion of NIR Sunlight with Neodymium‐Doped Glass Ceramics

“…ZBLAN (ZrF4‐BaF2‐LaF3‐AlF3‐NaF)‐based glasses and glass ceramics are suitable hosts for efficient rare‐earth (RE) emission and photoluminescence upconversion. The ubiquitous REs erbium and neodymium are efficient emitters when embedded into ZBLAN . A possible application of RE‐based upconversion in photovoltaics is to make NIR photons at energies below the silicon bandgap available for electrical power generation in Si‐based solar cells .…”

Raman spectra of barium halides in orthorhombic and hexagonal symmetry: Anab initiostudy

“…3,4 For high fluorescence efficiencies nonradiative losses in the RE host material can be reduced by using host materials with low phonon energies, e.g., fluorozirconate (FZ) glasses (< 590 cm −1 ). 5,6 If these glasses are additionally doped with Cl or Br ions the growth of nanocrystals during a subsequent annealing procedure is initiated. The BaCl 2 and BaBr 2 nanocrystals are appropriate hosts for the RE ions and improve the fluorescence efficiency of these systems further because of the very low maximum phonon energies.…”

“…Raman spectra of those barium halides are uncommon in literature because of the high hygroscopicity of these compounds. Raman spectra of hexagonal and orthorhombic BaCl 2 and BaBr 2 nanocrystals were measured recently by Pfau et al 6 So far, vibrational properties of hexagonal bulk crystals of BaCl 2 , BaBr 2 , and BaI 2 , as well as the orthorhombic BaI 2 , have not been determined because of their thermodynamic instability. 9,10 Theoretical considerations about phonons of barium halides were outlined until recently only for BaF 2 in the simpler cubic symmetry Fm3m.…”