Crystallization kinetics of glass microspheres with yttrium aluminium garnet (YAG) composition

Crystallization kinetics of Al2O3-26mol%Y2O3 glass and full crystallized transparent Y3Al5O12-based nanoceramic

“…The activation energies calculated from the slopes of the plots ln(β/(T p − T 0 ) n ) vs (1000/T p ) are 1535, 1541, and 1556 kJ⋅ mol − 1 for Kissinger, Augis-Bennett, and Ozawa models, respectively. The activation energy values of the AY26 glass obtained from these models are very close and much higher than that of previously reported stoichiometric YAG glasses (437 kJ⋅ mol − 1 reported by B. R. Johnson et al [23]; 578 ± 16 kJ⋅ mol − 1 reported by G. He et al [24]; 1100 ± 10 kJ⋅ mol − 1 reported by A. Prnová et al [25].) This result indicates that an excess of Al 2 O 3 in AY26 glass gives rise to its better thermal stability and higher sluggishness to crystallization than YAG glass.…”

“…The crystallization mechanism of stoichiometric Y 3 Al 5 O 12 glass has been deeply investigated in the last few decades, but opaque polycrystalline ceramics with submicron and micron YAG crystals have been usually obtained [23][24][25][26]. For instance, as reported by A. Prnová et al the apparent activation energy of glass microspheres with stoichiometric YAG composition was 1100 ± 10 kJ mol − 1 and a three-dimensional crystal growth was determined [25]. The presence of regularly spaced YAG crystals with size ≤ l μm was observed in the whole volume of fully crystalline microspheres.…”

Glass‐ceramic Ce3+‐doped YAG‐Al2O3 composites prepared by sintering of glass microspheres

“…The T g temperature roughly estimated from DSC also increased from 889, 890, 899, 902 to 913℃ with increasing Al 2 O 3 content starting from 80YAG–20Al 2 O 3 to 40YAG–60Al 2 O 3 composition. Based on our previous studies 31,32 and on phase evolution results from high‐temperature XRD (see discussion below), both observed exothermic effects correspond to two‐step crystallization of the YAG phase. In fact, the peak temperature of the second exothermic effect increased with increasing Al 2 O 3 content in glass, which points to the important role of diffusion in the glass during the crystallization process of the YAG phase from an amorphous matrix.…”

“…The XRD patterns were recorded in the temperature range from 800℃ up to 1500℃ with the step of 10℃ and in 2 θ range 25–47°, which covers typical diffractions of YAG and Al 2 O 3 phases. The first indication of the YAG phase crystallization was observed at a temperature of 920℃ when the most intensive YAG [0 2 4] diffraction at 2 θ = 33.394° appeared from a broad amorphous halo 27,31,32 …”

“…The precursor powders for flame synthesis were prepared by the modified Pechini sol–gel method, as described in detail in our previous works 31,32 …”