Formation and Properties of Ln‐Si‐O‐N Glasses (Ln = Lanthanides or Y)

Abstract

Homogeneous Y‐Si‐O‐N glasses containing 15 or 20 eq% nitrogen (N) were prepared from compositions with Y/Si ratios in the vicinity of that of the lowest eutectic point on the Y2O3–SiO2 phase diagram. The liquidus on the phase diagram shifted toward lower temperatures by incorporation of N. The density, the elastic moduli, and the glass transition temperature of the Y‐Si‐O‐N glasses increased with incorporation of N. This is due to the closer packing of atoms in the glasses by the substitution of N, which is in three‐fold coordination with Si, for O which is in two‐fold coordination, and the stronger covalent nature of the Si–N bond compared with the Si–O bond. The coefficient of thermal expansion of the Y‐Si‐O‐N glasses increased with increasing Y content, because the discontinuity of the glass network developed with increasing nonbridging anions by the introduction of Y. In contrast, the glass transition temperature and the elastic moduli increased with Y content due to the high coordination of Y for O, and the relatively high cationic field strength of Y. Furthermore, the effect of cationic field strength on properties of Ln‐Si‐O‐N glasses (Ln = lanthanides or Y) is discussed.

Thermal expansion and glass transition temperature of the rare-earth doped oxynitride glasses

“…The fact that ionic radius (and CFS) of Y lies between radii of Gd and Yb seems to be a coincidence. Thus, although hardness and some other properties of Y-glasses often fit the dependence on CFS for lanthanide-containing glasses, 13,15,17,19 Y belong into another group together with Sc. There are some experimental data supporting this conclusion.…”

“…2À7,11,12 Because of higher valence of nitrogen, partial substitution of oxygen by nitrogen in the network produces tighter and more linked structure. It results in linear increase in density, 4,10,13À17 hardness, 3,4,8,9,15,17 Young's modulus, 8,13,16À18 thermal expansion coefficient, 4,6,9,13,19,20 glass transition temperature, 4,6,9,13,19,20 viscosity 9,14,15,21 etc. For instance, adding 20 eq.% of N resulted in 33% increase in La-and 23% increase of elastic modulus in Lu-containing oxynitride glasses.…”

Structural characterisation of Er–Si–Al–O–N glasses by Raman spectroscopy

“…[2][3][4] A number of investigations have been carried out on bulk glass formation and properties in several M-Si-O-N and M-Si-Al-O-N systems where M is a modifying cation such as the alkaline earths (Mg, Ca, Ba) [5][6][7][8][9] or Y 5-7,10-15 and the rare earth lanthanides. [16][17][18][19][20][21][22][23][24] The first systematic studies 5,6,11 on the effect of replacing oxygen by nitrogen in oxynitride glasses reported that for all Mg-, Ca-, Y-and Nd-Si-Al-O-N glasses with constant cation ratios, incorporation of nitrogen resulted in increases in glass transition temperature (T g ), viscosity, hardness, refractive index, dielectric constant and ac conductivity. Viscosity increases by more than two orders of magnitude simply by replacing 18 e/o oxygen by nitrogen.…”

Viscosity and surface tension measurements of RE₂O₃–MgO–SiO₂ (RE=Y, Gd, Nd and La) melts

“…This causes substantial variations in the various properties (softening point, 12) glass transition temperature, [12][13][14][15][16][17][18][19] liquidus temperature, [20][21][22] elasticity modulus, 23) refractive index, 13,18,23) expansion coefficient, [13][14][15][16][17] hardness, Fumiyuki SHIMIZU, 1) Hirofumi TOKUNAGA, 2) Noritaka SAITO 2) and Kunihiko NAKASHIMA 2) 1) Production Department, Shoei Chemical Inc., 5-3, Aza-wakazakura, Fujinoki-machi, Tosu 841-0048 Japan. ).…”

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15,17,24,25) shear modulus, 12,14) Young's modulus 12,14,16) and density 14,15,17) ) of rare-earth containing oxide and/or oxynitride glasses that are the grain boundary phase of Si 3 N 4 ceramics sintered with rare-earth oxide additives, and thus, can also affect grain growth of b-Si 3 N 4 itself. However, to our best knowledge, there are no available data on the physical properties of rare-earth containing high temperature melts.

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