High temperature creep of La-monazite

Abstract

Abstract Compressive creep of La-monazite is investigated in the temperature range 1100 °C to 1500 °C. The study includes both high-purity single-phase material and material with excess phosphorus located in amorphous grain boundary phases. The results indicate that the presence of small amounts of excess P in polycrystalline LaPO4 has a large effect on microstructural stability and creep at high temperature. Materials with La/P ratio close to unity (within ∼500 ppm) show little grain growth at temperatures up to 1400 °C and deform by creep at rates similar to those of alumina and zirconia, with stress exponent ∼1. Materials containing excess P (as little as ∼1 %) show more rapid grain growth, higher creep rates, and cavitation during creep. The results are compared with creep rates of other refractory oxides and oxide fibers. Implications for the behavior of oxide composites containing La-monazite are considered.