Sintering behaviour and translucency of dense Eu2O3 ceramics
Eu2O3 is a technologically relevant material mainly because Eu3+ cations present an emission band centred in a primary color (red at 612 nm). However, reports on Eu2O3 ceramics are scarce. We investigate in this manuscript the sintering process in Eu2O3 ceramics. We reach the highest density ever reported in such ceramics. At such values of density, Eu2O3 becomes translucent, an unreported and surprising result taking into account the monoclinic symmetry of the compound (transparent ceramics are most commonly cubic). A systematic study of the sintering behaviour reveals that the combination of high-density with moderate grain growth that takes place at 1500 ºC is at the origin of the functional properties. Lower sintering temperatures do not yield the appropriate microstructure to support translucency. This constitutes a novel and important finding both fundamentally and from the applications viewpoint. Indeed, considering the fact that Eu2O3 is employed in optical applications and devices, translucency constitutes a highly appealing additional functionality.
Journal of the European Ceramic Society, Volume 34, Issue 7, July 2014, Pages 1803–1808.
Adrián Quesada, Adolfo del Campo, José F. Fernández.
Electroceramic Department, Instituto de Cerámica y Vidrio, CSIC, Kelsen 5, Madrid 28049, Spain.
Eu2O3 ceramics have been obtained at sintering temperatures of between 1000 °C and 1550 °C. X-ray diffraction and scanning electron microscopy, in combination with dilatometry experiments, allowed understanding the sintering behaviour. Moderate grain growth followed an efficient densification process between 1400 °C and 1550 °C, which yielded high-density ceramics with an average grain size of 4 μm. The ceramics had Young modulus of 125 GPa, in agreement with the previously published data. The dense Eu2O3 ceramics were translucent (35.1% transmittance at 800 nm of 0.8 mm thick discs), showing in addition a slightly pink colour. We propose that the combination of high density and an average grain size of 4 μm is responsible for this novel functionality.