KTb(MoO₄)₂ Green Phosphor with K⁺-Ion Conductivity: Derived from Different Synthesis Routes

Abstract

The influence of different synthesis routes on the structure and luminescent properties of KTb(MoO 4 ) 2 (KTMO) was studied. KTMO samples were prepared by solid-state, hydrothermal, and Czochralski techniques. These methods lead to the following different crystal structures: a triclinic scheelite-type α-phase is the result for the solid-state method, and an orthorhombic KY(MoO 4 ) 2 -type γ-phase is the result for the hydrothermal and Czochralski techniques. The triclinic α-KTMO phase transforms into the orthorhombic γ-phase when heated at 1273 K above the melting point, while KTMO prepared by the hydrothermal method does not show phase transitions. The influence of treatment conditions on the average crystallite size of orthorhombic KTMO was revealed by X-ray diffraction line broadening measurements. The electrical conductivity was measured on KTMO single crystals. The orthorhombic structure of KTMO that was prepared by the hydrothermal method was refined using synchrotron powder X-ray diffraction data. K + cations are located in extensive two-dimensional channels along the c-axis and the a-axis. The possibility of K + migration inside these channels was confirmed by electrical conductivity measurements, where strong anisotropy was observed in different crystallographic directions. The evolution of luminescent properties as a result of synthesis routes and heating and cooling conditions was studied and compared with data for the average crystallite size calculation and the grain size determination. All samples' emission spectra exhibit a strong green emission at 545 nm due to the 5 D 4 → 7 F 5 Tb 3+ transition. The maximum of the integral intensity emission for the 5 D 4 → 7 F 5 emission under λ ex = 380 nm excitation was found for the KTMO crashed single crystal.

K5Eu(MoO4)4 red phosphor for solid state lighting applications, prepared by different techniques

“…Luminescence properties are strongly dependent on various factors such as synthesis techniques, annealing temperature, grain diameter, size of coherent scattering regions (crystal size), and others. 34,35 In this work, we prepared K 5 Eu(MoO 4 ) 4 by various methods and tried to reveal the influence of synthesis techniques on material structure and luminescence properties.…”

K5Eu1–xTbx(MoO4)4 Phosphors for Solid-State Lighting Applications: Aperiodic Structures and the Tb3+ → Eu3+ Energy Transfer

“…Thus, the positions of the energy states for Tb 3+ and Eu 3+ contribute to the efficient transfer of energy from Tb 3+ to Eu 3+ . Earlier, the efficient energy transfer from Tb 3+ to Eu 3+ based on a dipole–dipole mechanism was found in other Mo-based phosphors. − …”

“…Eu 3+ -containing Mo-based materials with different crystal structures were investigated for their potential as red phosphors due to the efficient 5 D 0 – 7 F 2 transition of Eu 3+ ions. − , On the other side, the Tb 3+ ions are known as an excellent green-emitting activator due to the 5 D 4 → 7 F 5 transition. The usage of multiple activator ions, such as Eu 3+ and Tb 3+ , with the utilization of an energy transfer mechanism is an effective well-known strategy (the so-called co-doping strategy) for achieving a tunable multicolor emission inside a single phosphor host material. − The Eu 3+ and Tb 3+ co-doping pair is regarded as an “effective pair” in the energy transfer process from Tb 3+ to Eu 3+ found in Mo-based phosphors. − …”

KB3H8·NH3B3H7 Complex as a Potential Solid-State Electrolyte with Excellent Stability against K Metal

“…Research efforts are ongoing to develop the fast K-ion conducting SSE materials, mainly including oxides, − phosphidosilicates, antiperovskites, polymers, − and composites. − Currently, only a few K-ion SSEs have displayed ionic conductivities in a reasonable range for application in all-solid-state batteries (above 10 –4 S cm –1 ) at room temperature. For example, the T5 supertetrahedral phosphidosilicate KSi 2 P 3 displays a high bulk ionic conductivity of 2.6 × 10 –4 S cm –1 at 25 °C .…”