ISO/TC 298/WG 4 - Testing and Analysis

This document describes procedures for the determination of non-rare earth impurities in individual rare earth metals and their oxides through the use of inductively coupled plasma atomic emission spectroscopy (ICP-AES). Magnesium (Mg), aluminum (Al), silicon (Si), calcium (Ca) and iron (Fe) are included as non-rare earth impurity elements, and the measurement ranges for each impurity element are specified. The applicable measurement range (mass fraction %) of magnesium, aluminum, silicon and calcium is from 0,001 to 0,2, and that of iron is from 0,001 to 0,5. The verified measurement ranges in the interlaboratory tests are described later in this document.

This document specifies a gravimetric method for the determination of rare earth content in 11 kinds of individual rare earth metals (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium and yttrium) and their compounds, such as oxides, carbonates, hydroxides, oxalates, chlorides and fluorides. The determination ranges for the rare earth content in mass fraction are as follows: — rare earth metal: 98,0 % (mass fraction) to 99,5 % (mass fraction); — rare earth oxide: 95,0 % (mass fraction) to 99,8 % (mass fraction); — rare earth oxalate: 95,0 % (mass fraction) to 99,8 % (mass fraction); — rare earth fluoride: 75,0 % (mass fraction) to 90,0 % (mass fraction); — other compounds (i.e. rare earth hydroxide, rare earth chloride and rare earth carbonate): 40,0 % (mass fraction) to 70,0 % (mass fraction). It does not apply to individual rare earth metals and their compounds when: a) the matrixes of the sample are erbium, thulium, ytterbium and lutetium; b) the content of thorium or lead in the sample is greater than 0,1 % in mass fraction.

This document specifies a titration method for the determination of rare earth content in 15 kinds of individual rare earth metals (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and yttrium) and their oxides. The determination ranges for the rare earth content in mass fraction are as follows: — rare earth metal: 98,0 % (mass fraction) to 99,5 % (mass fraction); — rare earth oxide: 95,0 % (mass fraction) to 99,5 % (mass fraction). It does not apply to individual rare earth metals and their oxides when: a) the relative rare earth purity is less than 99,5 % in mass fraction; b) the total content of various (non-rare earth) metallic elements is greater than 0,5 % in mass fraction; c) the content of thorium, scandium or zinc is greater than 0,1 % in mass fraction.