Dense lanthanum silicate oxyapatite ceramics obtained by uniaxial pressing and slip casting

Abstract

Lanthanum silicate oxyapatite (LSO) is a promising ion conductive ceramic material, which has higher oxygen ion conductivity at intermediate temperatures (600-800 °C) compared to yttria-stabilized zirconia. Its mechanical properties, though important for any of its applications, have been scarcely reported. In this study, we compare apparent densification, open porosity and Vickers hardness of samples conformed by uniaxial pressing and slip casting and fired up to 1600 °C. Colloidal processing was optimized for slip casting in order to get high green densities. At sintering temperatures higher than 1400 ºC, both processing routes yielded comparable densities, although uniaxially pressed samples show slightly better mechanical properties, evidencing that slip cast ones already underwent a grain growth process.

Influence of the porosity caused by incomplete sintering on the mechanical behaviour of lanthanum silicate oxyapatite

“…Synthesis of the LSO powder was carried out the same way as in a previous study [26]. In essence, La(OH) 3 and SiO 2 powders were mixed and calcined thrice at 1400 °C for 10 h in air.…”

“…2. While it is commonplace to plot relative density, bulk density is shown because it is not possible to differentiate between LSO phases from an XRD pattern, as we have previously discussed [26]. However, taking into account that the density of La 9.33 (SiO 4 ) 6 O 2 is 5.32 g/cm 3 according to PDF 00-049-0443 and the density of La 10 (SiO 4 ) 6 O 3 is 5.61 g/cm 3 according to PDF 00-053-0291, we can limit the relative density of the most dense material, M15, to a range between 94% and 99% of theoretical density.…”