MONOPHASIC SILICA GLASSES WITH LARGE NEODYMIA CONCENTRATION

The use of one ideal candidate for high-powered lasers, neodymia-silica glass, is unfortunately limited by phase separation into undesirable Nd-rich crystalline droplets within an Nd-deficient matrix. Plasma CVD and sol-gel process using NdCl3 or Nd(NO3)3 as dopant both failed to produce single-phase Nd2O3-SiO2 glass when neodymia exceeded 5 wt%. Using Nd(COOCH3)3 and acetic acid hydrolysed tetraethlyl orthosilicate, the present authors produced monolithic glasses 10 (wt%) Nd2O3.90 SiO2 with no observable phase separation. Nd chloride doped gels, where the neodymium concentration increased from the interior to the surface, were much poorer in chemical homogeneity than Nd acetate doped gels of equivalent composition. Free salts of neodymium are responsible for causing the concentration gradient.