Outstanding optical temperature sensitivity and dual‐mode temperature‐dependent photoluminescence in Ho³⁺‐doped (K,Na)NbO₃–SrTiO₃ transparent ceramics

Abstract

High optical temperature sensing properties based on rare-earth-doped (K,Na) NbO 3 -based ferro-/piezoelectrics have attracted much attention due to their potential application in novel optoelectronic devices. Here, we fabricated Ho 3+ -doped (K 0.5 Na 0.5 )NbO 3 -SrTiO 3 transparent ceramics by conventional pressureless sintering. Their microstructures, transmittances, up-conversion photoluminescence, and optical temperature sensing properties have been characterized in details. Because of the cubic-like phase, dense, and fine-grained structure as well as relaxor-like feature, the ceramics exhibit high transmittance (~70%) in the near-infrared region. Owing to Ho 3+ , green and red up-conversion emissions have been observed, which can be easily modulated by temperature. The ceramics have stable emission colors (<200°C) and superior temperature-modulating emission color-tunable performance (>200°C). Furthermore, the temperature sensing behavior based on the thermally coupled levels ( 5 F 4 , 5 S 2 ) of Ho 3+ has been analyzed by a fluorescence intensity ratio technique. The transparent ceramics possess outstanding optical temperature sensitivity (~0.0096/K at 550 K), higher than most rare-earth-doped materials (e.g.

Effects of defect on thermal stability and photoluminescence in quenched Ho‐doped 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 lead‐free ceramics

“…8. When the ceramics samples are excited by 980 nm optical fiber laser, the electrons on the ground state 5 I 8 of Ho 3+ ions are excited to 5 I 6 via the ground state absorption (GSA) [39,40,41]. Then, a part of excited electrons on the 5 I 6 level will be further excited to the 5 F 4 / 5 S 2 level by excited-state absorption (ESA) and then generates green emission by radiative transition to 5 I 8 level.…”

Smart white lighting and multi‐mode optical modulations via photochromism in Dy‐doped KNN‐based transparent ceramics

“…As mentioned above, high‐temperature sintering and aliovalent ion‐doping in KNN‐based ceramics can generate a large number of vacancies and other derived defects, which are able to form color centers by the stimulation of external energy (such as illumination). In an ideal situation, the total energy of an incident light that goes through a material can be consumed by electron transition, light transmission, reflection or scattering, 29 as illustrated in the diagrammatic sketch of optical transmittance (Figure 4F). And the passing light can be partly scattered and absorbed by the color centers, leading to the reduction in the energy used for light transmission.…”

Optical temperature sensing and luminescent switching properties in Pr/Er‐doped (K0.5Na0.5)NbO3 materials

“…For KNN‐based materials, their ferroelectric and piezoelectric properties can be optimized by doping rare‐earth ions, and the luminescent properties of KNN materials can also be endowed . Meanwhile, optical temperature sensing properties of rare‐earth‐doped KNN materials have been widely investigated . However, most of KNN materials mentioned above are doped by single rare‐earth ions (or Yb 3+ ion as sensitizer).…”

“…14,15 Meanwhile, optical temperature sensing properties of rare-earth-doped KNN materials have been widely investigated. 16,17 However, most of KNN materials mentioned above are doped by single rare-earth ions (or Yb 3+ ion as sensitizer). And, the effects of dual lanthanide ion doping on optical temperature sensing properties in ferroelectric materials have been rarely reported.…”