Glass-to-Vitroceramic Transition in the Yttrium Aluminoborate System: Structural Studies by Solid-State NMR

Abstract

The crystallization of laser glasses in the system (B 2 O 3 ) 0.6 {(Al 2 O 3 ) 0.4-y (Y 2 O 3 ) y } (0.1 e y e 0.25) doped with different levels of ytterbium oxide has been investigated by X-ray powder diffraction, differential thermal analysis, and various solid-state NMR techniques. The homogeneous glasses undergo major phase segregation processes resulting in crystalline YBO 3 , crystalline YAl 3 (BO 3 ) 4 , and residual glassy B 2 O 3 as the major products. This process can be analyzed in a quantitative fashion by solid-state 11 B, 27 Al, and 89 Y NMR spectroscopies as well as 11 B{ 27 Al} rotational echo double resonance (REDOR) experiments. The Yb dopants end up in both of the crystalline components, producing increased line widths of the corresponding 11 B, 27 Al, and 89 Y NMR resonances that depend linearly on the Yb/Y substitution ratio. A preliminary analysis of the composition dependence suggests that the Yb 3+ dopant is not perfectly equipartitioned between both crystalline phases, suggesting a moderate preference of Yb to substitute in the crystalline YBO 3 component.

Characterization of the glass-to-vitroceramic transition in yttrium aluminum borate laser glasses using solid state NMR

“…As a consequence it seems that the entire yttrium inventory of the glassy precursor is distributed into the crystallization products YBO 3 and YAl 3 (BO 3 ) 4 , and no additional yttriumcontaining phase is formed. These findings are basically identical to those obtained for the VC-Yx series studied previously [41]. Nevertheless, 11 B TQ MAS and 11 B{ 27 Al} REDOR data could reveal the formation of an additional crystalline phase in which boron is expected to be coordinated by three oxygen atoms and closely interacting with aluminum.…”

“…12 (left part) illustrates the REDOR attenuation curves obtained for all of the vitroceramic samples. The data on VC-Al20 are slightly different from those discussed on VC-Y20 in reference [41], even though the compositions are identical. This difference may be attributed to the longer annealing times used in the present study as compared to Ref.…”

“…Additional spectroscopic resolution is provided by the 11 B TQ MAS NMR results (Fig. 8) [41]. Closer examination reveals an additional sharp signal in the F1 dimension of the spectra of all the samples investigated.…”

“…This difference may be attributed to the longer annealing times used in the present study as compared to Ref. [41], potentially resulting in higher crystallinity of the present samples, but also some B 2 O 3 loss owing to volatilization. For VC-Al30 and VC-Al40 the REDOR attenuations are found to be complete at longer dipolar evolution times, indicating that all of the B(3) units are locally in contact with 27 Al.…”

“…As shown in reference [41], 11 B{ 27 Al} REDOR experiments are useful for spectroscopically separating the fractions of boron atoms that do or do not interact with 27 Al. Fig.…”