Influence of sintering parameters on transparency of reactive SPSed Nd3+:YAG ceramics

Reactive SPS of Al2O3–RE:YAG (RE = Ce; Ce+Gd) composite ceramic phosphors

“…The existence of a positive thermal gradient towards the center of the sample is evident. Previously, the authors showed its presence by the example of reactive SPSed Nd:YAG [57] and TiO2−SrTiO3 systems [67]. The presence of stress gradients is unlikely due to the relatively low value of applied external pressure [68].…”

“…1). The darkening of the sample with the occurrence of a dark brown tint is often associated with an increase in the concentration of oxygen vacancies (color centers) during sintering in a vacuum [57]. The base colors for the relatively homogeneous Ce-doped and Ce,Gd-codoped samples (range 1400-1425°C) were green and brown, respectively.…”

“…SPS treatment is accompanied by the contamination of ceramic masses with carbon impurities, which can create serious problems for the final materials (among other things, lowers the PL quantum yield [11]). At the same time, the activation of carbon diffusion processes into ceramic bulks also intensify with an increase in the applied pressure during SPS [57]. Post-annealing in an oxygen atmosphere is commonly used as a baseline scenario aimed at removal of mechanical stresses, as well as the reducing the concentration of oxygen vacancies and carbon particles in SPSed ceramics [57,78,79].…”

“…Among these approaches, SPS is a proven pressure-assisted technique for relatively fast and nearnet-shape fabrication of fine-grained ceramic materials with some inherent residual porosity. At the same time, Kosyanov et al previously proposed and successfully tested a simple, cost-effective, and innovative method to obtain ultrafine-grained RE 3+ :YAG optical ceramics via reactive SPS of Y2O3-RE2O3-Al2O3 oxide powder systems [56,57]. This "one-step" method additionally allows the implementation of phase transformations as one of the main driving forces of sintering to obtain uniform, highly dense garnet-type structure at relatively low temperatures and a short sintering time.…”

Effect of Ceramic Formation on the Emission of Eu3+ and Nd3+ Ions in Double Perovskites

“…The main advantage of this method is that it allows a rapid heating rate up to 200–300 °C/min; therefore, the waiting time for elevating the temperature is shortened. Recently, transparent ceramics sintered by SPS method have been extensively investigated [ 6 , 19 , 20 , 21 , 22 , 23 ]. The temperature and pressure parameters play an important role in the quality of ceramics, especially transparency.…”