Machinable Ceramics Containing Rare‐Earth Phosphates

Abstract

Two-phase composites consisting of LaPO 4 or CePO 4 and alumina, mullite, or zirconia were found to be machinable; i.e., they can be cut and drilled using conventional tungsten carbide metal-working tools. Single-phase LaPO 4 was also machinable. Measurements of drilling rates, grinding rates, and normal forces are used to compare the ease of machining in these materials and in a conventional machinable glass-ceramic material, and to provide preliminary information on the relation between microstructure and machining properties. In Hertzian contact experiments these materials showed extensive nonlinear behavior associated with a damage zone beneath the contact site, similar to other machinable ceramics. Mechanisms of material removal are discussed.

Thermal evolution, second phases, and sintering behavior of LaPO4·nH2O nanorods prepared by two different chemical synthesis routes

“…Among the many REPO 4 phases, LaPO 4 stands out for its broader range of applications in different areas of technological interest [4][5][6][7][8][9]. In addition, monoclinic monazite-type LaPO 4 presents very high melting point (4 2000 1C), extremely low water solubility and chemical and thermal stability and, therefore, is currently under consideration as ceramic matrix for immobilizing high-level radioactive waste [4,7].…”

“…In addition, monoclinic monazite-type LaPO 4 presents very high melting point (4 2000 1C), extremely low water solubility and chemical and thermal stability and, therefore, is currently under consideration as ceramic matrix for immobilizing high-level radioactive waste [4,7]. Doped with cerium and terbium, bulk LaPO 4 is a commercially applied lamp phosphor [10], while if doped with strontium, becomes a high-temperature proton conductor [11,12]. In addition, it has been recently proposed as component of a new class of machinable ceramics based on two-phase mixtures of refractory oxides (Al 2 O 3 , ZrO 2 , etc.)…”

Preparation and mechanical properties of machinable alumina/mica composites

“…by hot pressing and spark plasma sintering, our machinable composites containing mica 8,9 can be fabricated without the special sintering apparatuses. Moreover, comparing with machinable composite containing phosphates, [3][4][5]13 our machinable composites containing mica 8,9 have a possibility of low-temperature sintering due to sintering through the liquid phase formed by melting of the additive glass. Thus, the fabrication at low temperatures using conventional apparatuses is the merit of our machinable composites.…”

Preparation of CePO4-coated zirconia ceramics and their mechanical behavior

“…Rong et al produced machinable dental zirconia ceramics by the addition of CaO-Al 2 O 3 -SiO 2 sintering aids [11]. Davis et al reported on the preparation and preliminary testing of metallic oxide/rare earth phosphates composite ceramics [12]. In comparison, for the second method, some different preparation processes can be used and it is easier to achieve uniform distribution of the two phases.…”