Formation and stability of Gd, Y, Yb and Lu disilicates and their solid solutions

High temperature water vapour corrosion of rare earth disilicates (Y,Yb,Lu)2Si2O7 in the presence of Al(OH)3 impurities

“…3 However, in previous studies we found the γ polymorph of Y 2 Si 2 O 7 to be stable between approximately 1320 • C and ≥1600 • C with a sluggish transformation kinetics down to 1200 • C. 21,22 Thus this material could behave well in real applications. Furthermore, at least the solid solution materials with Y ≤ 50 mol% + Yb or Lu are not expected to show any polymorphism in a temperature range between <1000 • C and approx.…”

Growth of bulk gadolinium pyrosilicate single crystals for scintillators

“…In accordance with [11], melt composition may be shifted from the stoichiometric ratio to the SiO 2 excess up to 4 mol% (concentration corresponding to the position of the peritectic point at Gd 2 O 3 -SiO 2 phase diagram [8]). At heavy doping by Ce, the average rare-earth cation radius increases in accordance with relative content of each lanthanide element [15], and position of the peritectic point relatively to the stoichiometric composition should change. Therefore, the required SiO 2 excess in starting material depends on the averaged radius of lanthanides in the current composition.…”

“…Therefore, the required SiO 2 excess in starting material depends on the averaged radius of lanthanides in the current composition. The amount of excess was determined on the base of phase diagram for the certain trivalent lanthanide [8], which ionic radius corresponds to the averaged radius of different lanthanides in the starting material calculated by the formulae (3) [15] (R RE is the rare-earth ionic radii and C RE is the molar ratio of rare-earth elements)…”

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

“…The cation sizes for Ho, Er, Tm, Yb, Lu, and Y are 0.90 Å , 0.89 Å , 0.88 Å , 0.868 Å , 0.861 Å , and 0.89 Å , respectively. 16,17 The weighted average ionic size is 0.87 Å , comfortably below our stability criterion of 0.88 Å .…”