Ceramics-Silikáty 52, (2) 109 - 114 (2008)

The work deals with alternative way of preparation of binary aluminate glasses by flame synthesis of glass microspheres from powder precursors, and their subsequent sintering under mechanical pressure in viscous flow regime and in the temperature interval between the glass transition temperature T_g and the onset of crystallization temperature T_x. The flame synthesis yielded the microspheres with diameters between 10 and 40 µm: seven compositions in the pseudo binary system Al₂O₃–Y₃Al₅O₁₂ (YAG) were prepared. Except of the eutectic composition, all other compositions were partially crystalline, consisting of amorphous yttrium aluminate matrix containing YAG and α-Al₂O₃ as the main crystalline phases. The presence of crystalline phases was due to insufficient melting of the precursor powder in the flame and could be partially eliminated by re-melting. The results of DTA indicated hight tendency of the prepared glasses to crystallization, with narrow interval of 50 °C between the T_g and T_x. The sintering of microspheres under applied mechanical pressure of 30 MPa resulted in white non transparent glasses with residual porosity P = 0.12, and increased content of crystalline phases as the result of secondary crystallization of glasses during sintering