Novel amorphous precursor densification to transparent Nd:Y2O3 Ceramics

A novel approach of neodymium ion doped yttrium oxide (Nd:Y2O3) amorphous precursor compaction and sintering is being reported for the first time. Precursor of 2 at.% Nd3+ doped Y2O3 was synthesized by gelation of sol of yttrium and neodymium nitrates with L-alanine at 80 degrees C for 16 h followed by gel combustion in microwave. A part of microwave precursor was heat treated at 700 degrees C for 5 h to give the partially crystalline Nd:Y2O3 amorphous precursor. Thermogravimetric analysis (TGA) of partially crystalline amorphous precursor of Nd:Y2O3 gave 8.5% total weight loss indicating removal of maximum organics. X-Ray diffraction (XRD) showed broad peaks indicating incomplete crystallization of cubic Nd:Y2O3. Morphology was found to be close to spherical with particles in size range 17-19 nm by TEM. Another part of microwave precursor on calcination at 1000 degrees C for 3 h led to formation of fully crystalline Nd:Y2O3 with particles in size range of 35-85 nm. Both partially crystalline amorphous precursor and fully crystalline Nd:Y2O3 were compacted at 400 MPa by cold isostatic press and sintered at 1750 degrees C for 10 h under vacuum (10(-5) mbar). The partially crystalline Nd:Y2O3 amorphous precursor densified to 99% with 65% transmission at 2500 nm (0.5 mm thickness) compared to 96% densification with 34% transmission for fully crystalline Nd:Y2O3 without any sintering aids. Retention of cubic phase purity of Y2O3 was observed in both the ceramic pellets post sintering by XRD. Good grain fusion with grain growth to <= 2 mu m was observed by scanning electron microscope (SEM) for partially crystalline Nd:Y2O3 amorphous precursor. Thus partially crystalline Nd:Y2O3 amorphous precursor nanopowders, with homogeneous close to spherical fine particles and high reactivity due to ionic mobility of amorphous phase, led to better densification. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.