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Sm‐Doped LaSi 3 N 5 : Synthesis, Computed Electronic Structure, and Band Gaps
Author(s) -
Ibrahim Ismail A.M.,
Lenčéš Zoltán,
Benco Ľubomír,
Hrabalová Monika,
Šajgalík Pavol
Publication year - 2014
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.12968
Subject(s) - doping , band gap , electronic structure , materials science , hybrid functional , density functional theory , ab initio , condensed matter physics , stoichiometry , crystallography , atomic physics , chemistry , physics , computational chemistry , organic chemistry
LaSi 3 N 5 ‐based phosphor doped with Sm was prepared by the nitridation of LaSi‐Si‐Si 3 N 4 ‐ Sm 2 O 3 powder mixture. The emission spectrum shows two main bands with maxima at 595 nm in the orange region and at ~650 nm in the red region. The excitation spectrum of Sm‐doped LaSi 3 N 5 shows a maxima at 585, 570, and 405 nm. First‐principles density‐functional theory calculations were performed using Vienna ab initio simulation package to enhance the understanding of the electronic structure of the stoichiometric LaSi 3 N 5 and Sm‐doped LaSi 3 N 5 . The electronic structure and band gaps were calculated in 2 × 1 × 2 supercell with 144 atoms using the more precise screened Coulomb hybrid functional HSE06. Both La 3+ / Sm 3+ and La 3+ / Sm 2+ substitutions were calculated. The calculated band gap of Sm(III)‐doped LaSi 3 N 5 is 2.01 eV , in reasonable agreement with the experimental value of 2.12 eV , but corresponds to the unrealistic transition between the N, Si p states, and unoccupied Sm 4 f states. The band gap of 1.43 eV calculated for Sm(II)‐doped LaSi 3 N 5 is smaller than the available experimental value, but corresponds to the correct transition between nonbonding Sm 4 f states and empty La 5 d states. Optical properties are found to be governed by f electrons of the Sm(II) dopant.