Effect of Ca ²⁺ and Mg ²⁺ ions on the sintering and spectroscopic properties of cr‐doped yttrium aluminum garnet ceramics

Abstract In this work, we investigated the effects of Ca ²⁺ and Mg ²⁺ ions and annealing temperature on the spectroscopic parameters of chromium‐doped yttrium aluminum garnet ceramics (Cr:YAG). Samples were obtained with either a separate or a simultaneous addition of calcium and magnesium oxides. To achieve this, aqueous suspensions were prepared using Y ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ , MgO, and CaO high‐purity powders as raw materials. The obtained suspensions were freeze‐granulated, pressed into pellets, debinded, and subjected to reactive sintering in vacuum at 1715°C for 6 h. Each material was annealed in air with temperatures between 1300 and 1700°C. Samples were also compared to Cr:YAG ceramics with the addition of silica as a sintering aid. All the materials obtained were then exposed to 445 nm excitation, and emission spectra in the visible and infrared wavelengths were recorded. The results showed that the emission spectra of Cr:YAG ceramics varied according to the annealing conditions: as‐sintered samples exhibited strong emissions of around 680 nm and, after air annealing, of around 1400 nm. This phenomenon is attributed to the Cr ³⁺ →Cr ⁴⁺ transition. Samples doped solely with MgO exhibited the highest emission intensity in the infrared region. Thus, Mg ²⁺ ions provided the best conversion efficiency of chromium ions.