New structural effects in SrMoO4:Tm3+/Ho3+ crystals

Abstract

Rare-earth doping of strontium molybdate, SrMoO₄, allows the combination of laser generation of light and its SRS conversion. The RE³⁺ introduction into the Sr²⁺Mo⁶⁺O₄ matrix must inevitably lead to the appearance of point defects that will affect the possibility of the effective use of the material. In this work, we report comprehensive structural research of SrMoO₄ single crystals both nominally pure and doped with different Tm³⁺ and Ho³⁺ concentrations, undertaken for the first time, using X-ray single crystal and powder diffraction (crystal structure), EXAFS/XANES (local structure), and optical spectroscopy. The compositions of the grown crystals are established for the first time. Introduction of RE³⁺ ions in the form of RE³⁺Nb⁵⁺O₄ leads to partial substitution of Mo⁶⁺ ions by Nb⁵⁺ along with the main location of Nb⁵⁺ ions in the interstitial sites near the defect Mo⁶⁺ sites with the formation of their own distorted tetrahedra. Dopant ions either replace partially the Sr²⁺ ions (Ho³⁺ ions) or are located in the interstitial sites near the defect Sr²⁺ sites (Tm³⁺ ions). The effective distribution coefficients of the dopants are determined.