Luminescence Mechanistic Study of BaLaGa3O7:Nd Using Density Functional Theory Calculations

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Lanthanum Gallium Oxide doped with Neodymium (BaLaGa3O7:Nd or BLGO:Nd) has been explored for laser crystal applications for approximately 30 years.
• Understanding the fundamental luminescence mechanisms is crucial for optimizing its performance in laser devices.

Purpose of the Study:

• To elucidate the luminescence mechanism of BLGO:Nd using first-principles density functional theory (DFT) calculations.
• To investigate the influence of intrinsic defects and co-doping on the optical properties of BLGO:Nd.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model the electronic structure and optical properties.
• Structural optimization of supercells was performed to determine equilibrium geometries.
• Electronic structures of the BLGO host, BLGO:Nd phosphor, and defect-containing models were analyzed.

Main Results:

• Single intrinsic defects in BLGO minimally impact light emission, despite creating impurity levels within the band gap.
• Luminescence in BLGO:Nd originates from Nd ions, with parity-forbidden 4f-4f transitions becoming partially allowed due to 4f-5d configuration mixing.
• Electronic transitions between occupied 4f and empty 4f-5d states are electric-dipole-allowed, enabling light emission.
• Neighboring intrinsic defects play a minor role, primarily in prolonging decay time.
• Theoretical analysis suggests co-doping with Terbium (Tb) could enhance luminescence due to favorable impurity orbital distribution.

Conclusions:

• The luminescence mechanism in BLGO:Nd is primarily driven by Nd 4f electron transitions facilitated by 4f-5d mixing.
• Co-doping strategies, particularly with other lanthanide ions like Tb, show theoretical promise for improving BLGO:Nd luminescence.
• This study provides theoretical guidelines for designing superior luminescent materials based on the BLGO host.