Custom-built thermometry apparatus and luminescence intensity ratio thermometry of ZrO₂:Eu³⁺ and Nb₂O₅:Eu³⁺

A complete apparatus for luminescence thermometry has been built comprising a programmable hot-plate up to 400 °C, a hot/cold plate 0 °C–80 °C, a control circuit with thermocouple feedback, a platinum resistance thermometer and an oven for calibration. An original design allowed us to build the apparatus for under 100 $, considerably less than for the commercial equipment. The apparatus must be used with an optical fiber bundle attached to a spectrofluorometer. It is tested for stability and on ZrO₂:Eu³⁺ and Nb₂O₅:Eu³⁺ samples prepared by a plasma electrolytic process. The tests showed the high stability of the temperature-controlled surfaces. The thermometric properties of the investigated material were tested by the luminescence intensity ratio method of ⁵ D ₁  →  ⁷ F ₁ and ⁵ D ₀  →  ⁷ F ₂ transitions. The calculated relative sensitivities of Nb₂O₅:Eu³⁺ and ZrO₂:Eu³⁺ are 3.17% K⁻¹ and 3.07% K⁻¹ at 290 K, respectively, and 0.0012 K⁻¹ at 453 K and 0.000 12 K⁻¹ at 445 K are the calculated absolute sensitivity values, respectively. Nb₂O₅:Eu³⁺ has shown good thermometric properties up to 180 °C, while ZrO₂:Eu³⁺ is a promising temperature sensor phosphor for higher temperature measurements. (paper)