Anomalous densification behavior of Al2O3–Cr2O3 system

• Anomalies in densification behavior of Al2O3–Cr2O3 system were observed.
• Al2O3–Cr2O3 solid solution formation starts at 1400 °C and associated with endothermic peak.
• Endothermic solid solution formation partly absorbs the supplied heat energy which eventually retards the densification.
• Lattice parameters are consistent with solid solution formation.

Densification behavior of (Al1 − xCrx)2O3 (where, x = 0, 0.1, 0.3, 0.5) compacts in the temperature range 1000–1700 °C under reducing condition were studied. Up to 1300 °C, densification behavior followed the normal trend, i.e., bulk density increases with increase in Cr2O3 content. Anomaly in the densification behavior was observed from 1400 °C onwards. Al2O3 samples showed high densification; but the addition of 10 mol% Cr2O3 resulted in a sharp decrease in densification; while further Cr2O3 addition showed a steady rise in densification. XRD studies revealed the solid solution formation starts at 1400 °C. A broad endothermic peak at around 1400 °C in DTA thermogram corresponds to the formation of solid solution which actually absorbs extra heat energy resulting less dense Al2O3–Cr2O3 compacts. The average grain size of sintered Al2O3–Cr2O3 samples increases with increase in Cr2O3 content.