Phosphorescence in Mn4+-Doped R+/ R2+ Germanates (R+ = Na+ or K+, R2+ = Sr2+)

Sergei A Novikov; Yimin Lu; Weiguo Zhang; P Shiv Halasyamani; Shruti Hariyani; Jakoah Brgoch; Vladislav V Klepov; Hans-Conrad Zur Loye; Yurij Mozharivskyj

doi:10.1021/acs.inorgchem.2c01364

Phosphorescence in Mn⁴⁺-Doped R⁺/ R²⁺ Germanates (R⁺ = Na⁺ or K⁺, R²⁺ = Sr²⁺)

Inorg Chem. 2022 Jun 20;61(24):9364-9374. doi: 10.1021/acs.inorgchem.2c01364. Epub 2022 Jun 8.

Authors

Sergei A Novikov¹, Yimin Lu¹, Weiguo Zhang², P Shiv Halasyamani², Shruti Hariyani², Jakoah Brgoch², Vladislav V Klepov³, Hans-Conrad Zur Loye³, Yurij Mozharivskyj¹

Affiliations

¹ Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada.
² Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204, United States.
³ Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter Street, Columbia, South Carolina 29208, United States.

PMID: 35675534
DOI: 10.1021/acs.inorgchem.2c01364

Abstract

Single crystals of three new compounds, Na_0.36Sr_0.82Ge₄O₉ (1, proposed composition), Na₂SrGe₆O₁₄ (2), and K₂SrGe₈O₁₈ (3), were obtained and characterized using single-crystal X-ray diffraction. Their structures contain three-dimensional (3D) anionic frameworks built from GeO₄ and GeO₆ polyhedra. The presence of octahedral Ge⁴⁺ sites makes the new phases suitable for Mn⁴⁺ substitution to obtain red-emitting phosphors with a potential application for light conversion. Photoluminescence properties of Mn⁴⁺-substituted Na₂SrGe₆O₁₄ (2) and K₂SrGe₈O₁₈ (3) samples were studied over a range of temperatures, and red light photoluminescence associated with the electronic transitions of tetravalent manganese was observed. The Na₂SrGe₆O₁₄ (2) phase was also substituted with Pr³⁺ on the mixed Na-Sr site similar to the previously studied Na₂CaGe₆O₁₄:Pr³⁺. The red emission peak of the Pr³⁺ activator occurs at a shorter wavelength (610 nm) compared to that of Mn⁴⁺ (662-663 nm). Additionally, second harmonic generation (SHG) data were collected for the noncentrosymmetric Na₂SrGe₆O₁₄ (2) phase, indicating weak SHG activity. Diffuse reflectance spectroscopy and density of states calculations were performed to estimate the band gap values for pristine Na₂SrGe₆O₁₄ (2) and K₂SrGe₈O₁₈ (3) phases.