Abstract
In this paper the luminescence of the scheelite-based CaGd₂(₁-x)Eu₂x(WO₄)₄ solid solutions is investigated as a function of the Eu content and temperature. All phosphors show intense red luminescence due to the ⁵D₀ - ⁷F₂ transition in Eu³⁺, along with other transitions from the ⁵D₁ and ⁵D₀ excited states. For high Eu³⁺ concentrations the intensity ratio of the emission originating from the ⁵D₁ and ⁵D₀ levels has a non-conventional temperature dependence, which could be explained by a phonon-assisted cross-relaxation process. It is demonstrated that this intensity ratio can be used as a measure of temperature with high spatial resolution, allowing the use of these scheelites as thermographic phosphor. The main disadvantage of many thermographic phosphors, a decreasing signal for increasing temperature, is absent.
Highlights
Scheelites are A1- BO4 compounds (A = alkali, alkaline-earth or rare-earth element, B = Mo,W and some other tetrahedrally coordinated cations; denotes a cation vacancy) in which broad possibilities of isovalent and heterovalent cation substitutions result in a range of compounds with interesting optical properties, good stability and simple preparation [1,2,3].Upon heterovalent substitution at the A sublattice, the charge balance can be maintained by the introduction of cation vacancies, giving rise to compositions characterized by a (A +A’):(BO4 + B’O4) ratio different from 1:1
This paper describes the temperature dependent luminescence properties of the CaGd2(1-x)Eu2x (WO4)4 (x = 0 to 1, = vacancy) solid solutions and discusses their potential application as a thermographic phosphor
We investigated the temperature dependence of both the luminescence and the decay pathways intense red light odfomCianGadte2d(1-bx)yEuth2xe(W5DO0 4–)47Fsc2hteraenlisteitsioinn and emission spectra
Summary
This paper describes the temperature dependent luminescence properties of the CaGd2(1-x)Eu2x (WO4) (x = 0 to 1, = vacancy) solid solutions and discusses their potential application as a thermographic phosphor. Most research focused on Dy3+ or Sm3+ as more suitable thermographic rare earth activators, using the temperature dependence of the intensity ratio of different emission lines [24,25,26,27,28]. In this paper it will be shown that in the studied scheelite energy level of Eu3+ is materials, the varying intensity ratio of sensitive enough for use as temperature the emission of the 5D0 and 5D1 sensor. The temperature map obtained by using the 5D0 to 5D1 intensity ratio showed high spatial resolution, in addition to an excellent correspondence with the temperature map recorded by more common infrared thermography
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