Volume and surface photoluminescence of congruent and stoichiometric lithium niobate crystals obtained using various technologies was studied. The luminescence intensity of the stoichiometric crystal was less than that of the congruent one. Volume luminescence of the crystals was mainly caused by Nb_Li defects while luminescence quenching of the near-surface layer was observed in the long-wavelength spectral region (>500 nm) because of energy scattering in crystal-lattice vibrations and increased luminescence intensity of the \( {\mathrm{Nb}}_{\mathrm{Nb}}^{4+}-{\mathrm{O}}^{-} \) pair. Luminescence bands with maxima at 426 and 446 nm were caused by complex defects in the form of electron–hole pairs \( {\mathrm{Nb}}_{\mathrm{Nb}}^{4+}-{\mathrm{O}}^{-} \) in which the Nb atom was bound to oxygen atoms by covalent and ionic bonds. An increase of the Li/Nb ratio led to a shift of the luminescence bands to shorter wavelengths and a change of the fundamental absorption edge of the studied crystals.

中文翻译：

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各种技术制备的名义纯铌酸锂单晶的光致发光

研究了使用各种技术获得的全同和化学计量铌酸锂晶体的体积和表面光致发光。化学计量晶体的发光强度小于全同晶体的发光强度。晶体的体积发光主要是由Nb _Li缺陷引起的，而在长波长光谱区域（> 500 nm）中观察到了近表层的发光淬灭，这是由于晶格振动中的能量散射和增强的发光强度所致。\（{\ mathrm {Nb}} _ {\ mathrm {Nb}} ^ {4 +}-{\ mathrm {O}} ^ {-} \）对。426和446 nm处最大的发光带是由电子-空穴对形式的复杂缺陷引起的\（{\ mathrm {Nb}} _ {\ mathrm {Nb}} ^ {4 +}-{\ mathrm {O }} ^ {-} \）其中Nb原子通过共价键和离子键与氧原子键合。Li / Nb比的增加导致发光带向较短波长的移动以及所研究晶体的基本吸收边的变化。