Abstract
As a typical and commercial nonlinear optical (NLO) material, LiNbO3 usually suffers from non-stoichiometric compositions, but the role of non-stoichiometry in second harmonic generation (SHG) remains unclear. In this study, we prepared non-stoichiometric LiNbO3 with a Li mole percentage amount covering critical ranges from 47 to 50. We found that a 47 mol % Li amount can remarkably weaken the SHG response by 50% without an obvious change of the band gap. A detailed structural analysis indicates that reducing the Li content brings anti-occupied Nb (NbLi4·) together with Li vacancies (VLi′), which decreases local distortions and local polarizations of both NbO6 and LiO6 octahedra and ultimately lead to the decline of the SHG response. Such effects are discussed in terms of the looser and less anisotropic structure character of LiNbO3. The above results are supported by joint synchrotron X-ray/neutron diffraction, atomic pair distribution function (PDF) analysis, and theoretical calculations. These insights are helpful to the future design of functional materials in non-stoichiometric compositions.
Original language | English |
---|---|
Pages (from-to) | 14735-14741 |
Number of pages | 7 |
Journal | Journal of Physical Chemistry C |
Volume | 126 |
Issue number | 34 |
DOIs | |
State | Published - Sep 1 2022 |
Funding
This research was supported by National Key R&D Program of China (no. 2020YFA0406202), National Natural Science Foundation of China (nos. 22090042, 21731001, and 21971009), and the Fundamental Research Funds for the Central Universities, China (nos. FRF-IDRY-19-018 and FRF-BR-19-003B). Neutron pair distribution function (nPDF) data were collected on the nanoscale-ordered material diffractometer (NOMAD) at the Center for Neutron Research at the National Institute of Standards and Technology (USA) (proposal no. 26734.1). X-ray total-scattering data were performed at the BL44B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI; proposal nos. 2021A1145 and 2021A1129). We thank Shihang Chu for the help in sample synthesis and SHG characterizations.