Mechanical attrition of lanthanum hydroxide with hydrogen gas followed by sintering.

In Indonesia, the use of monazite has been carried out for the rare earth processing industry by PT. Timah (Persero) Tbk with raw material in the form of tin mining waste. The pilot plant produces rare earth metal products in the form of hydroxides, such as lanthanum hydroxide La(OH)₃, with a price range of US$ 230 per kg. Application of La(OH)₃ includes water treatment, specialty glass, catalyst, optical coating, gas-exhaust convector, hydrogen storage material, superconductor, and dielectric material. This research was intended to specifically ball-mill lanthanum hydroxide (La(OH)₃) with hydrogen gas followed by sintering and to characterize the product materials. The expected yield of this synthesis was material for the superconducting application. The sintering temperature was pre-determined based on a differential scanning calorimeter (DSC) test, which was 550°C for 1 hour. The product characterization included x-ray diffraction (XRD), particle size analysis (PSA), and scanning electron microscopy (SEM). Lanthanum di-hydride (LaH₂) and lanthanum oxide (La₂O₃) were obtained as the products of this ball-milling, with the final compositions of 91.1 wt.% and 8.9 wt.%, respectively. The average particle size of the LaH₂ and La₂O₃ powder mixture was 190.3 nm, downsized from 323.7 nm of La(OH)₃ through the ball-milling process. SEM observation for the ball-milling product before sintering indicated the presence of particle aggregations. The increase in La₂O₃ content after sintering induced a higher crystallite strain of 2.0±0.1% compared to that after ball-milling. [ABSTRACT FROM AUTHOR]