Monotectic crystallization of melts in the ZrO2-Al2O3 system

Abstract

The morphology of the crystalline phases prepared at different cooling rates, temperatures, and compositions of melts in the ZrO 2 -Al 2 O 3 system is investigated. It is established that both the quenched and slowly crystallized samples containing 35-70 wt % ZrO 2 have a submicron structure. Outside this concentration range, the ingots have a zonal structure: the peripheral region is formed by large baddeleyite crystals (at a ZrO 2 content higher than 70 wt %) or corundum crystals (at a ZrO 2 content lower than 30 wt %). This character of the crystallization confirms the presence of the phase separation (liquid immiscibility) region in melts of this system. A variant is proposed for the phase diagram of the system under investigation.

Phase separation in melts of the ZrO2-Al2O3 system

“…An analysis of the quenched rod samples in our earlier work [2] and in this study demonstrates that the crystallization in the ZrO 2 -Al 2 O 3 system is characterized by specific features due to the presence of the liquid-liquid phase separation region. It should be noted that these features differ from those observed in crystallization of melts in systems with a complete miscibility in the liquid state.…”

“…However, the data on the phase diagram of this system are contradictory (see discussion in [1,2]). In [1,2], it was experimentally revealed that the liquid-liquid phase separation region exists in the ZrO 2 -Al 2 O 3 system. In the present study, we investigated the crystallization of melts in the ZrO 2 -Al 2 O 3 system with the aim of elucidating the mechanism of liquid-liquid phase separation.…”

Amorphous zones in flame sprayed alumina–titania–zirconia compounds

“…In the glass-ceramic system keatite mixed crystal ZrTiO 4 is formed in the presence of TiO 2 and ZrO 2 [50]. Thus an influence by the nucleation of ZrO 2 or various Zirkoniumtitanates respectively in this ternary system is very likely to appear [34,51,52]. The effect of spinodal demixing might provide embryonic crystals inducing nucleation during the rapid cooling.…”

Investigation of Physical and Chemical Processes of Formation of Composite Materials with Specified Structural Phase Characteristics

“…The existing classifications of eutectic structures are mostly based on dependence of the morphological and dimensional features of the co-crystallizing phases on the cooling conditions of the melt during its crystallization [12]. It was established [13,14] that the preparation of the finely dispersed eutectics (fine-grained phase mixtures) is possible at cooling rates ~ 10 6 °/С and higher.…”