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DOE OSTI2020

Materials Data on K2SrP2O7 by Materials Project

K2SrP2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.77–3.34 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.81–3.34 Å. Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Sr–O bond distances ranging from 2.48–2.58 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent SrO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–53°. There are a spread of P–O bond distances ranging from 1.53–1.66 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with three equivalent SrO6 octahedra and a cornercorner with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–46°. There is three shorter (1.53 Å) and one longer (1.67 Å) P–O bond length. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent K1+, one Sr2+, and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two P5+ atoms. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three K1+, one Sr2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three K1+, one Sr2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent K1+, one Sr2+, and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to three K1+, one Sr2+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to two K1+, one Sr2+, and one P5+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Heterovalent Substitution of K 2 SrP 2 O 7 :Cr 3+ to Achieve Anti-Thermal-Quenching Broadband Near-Infrared Luminescence

Broadband near-infrared (NIR) light sources based on phosphor-converted light-emitting diodes are highly desirable for biochemical analysis and medical diagnosis applications. However, thermal quenching remains a demanding challenge for developing efficient NIR phosphors. Herein, we report the enhancement of both quantum efficiency and thermal stability in Cr 3+ -activated K 2 SrP 2 O 7 phosphors through a heterovalent substitution strategy by replacing Sr 2+ with Al 3+ in K 2 Sr 1–x Al x P 2 O 7 (0.05 ≤ x ≤ 0.2) to obtain optimized broadband NIR emission. Structural modulation via Al 3+ substitution leads to the optimized composition, K 2 Sr 0.88 Al 0.1 P 2 O 7 :0.02Cr 3+ , which emits across a broad NIR range of 650–1100 nm peaking at 807 nm with a full width at half-maximum of ∼130 nm under 448 nm excitation. Remarkably, its emission intensity at 150 °C remains 120% of the initial value at room temperature, demonstrating a rare antithermal-quenching behavior. Temperature-dependent XRD studies further reveal that Al 3+ substitution effectively suppresses lattice expansion at elevated temperatures, indicating enhanced lattice stability under thermal excitation. Detailed structural and spectral analyses show that the substitution enhances local site symmetry, reduces electron–phonon coupling, increases thermally induced absorption probability, and fortifies energetic barriers against nonradiative transitions. These synergistic effects collectively endow this NIR phosphor with a superior thermal stability. Furthermore, NIR light-emitting diodes fabricated with this phosphor exhibit strong potential for applications in information identification, nondestructive detection, and night vision technologies. This study demonstrates a local structure engineering strategy for designing thermally robust Cr 3+ -activated NIR phosphors, offering valuable insights into material discovery and NIR spectroscopy device development.

Cr3+↗