Novel amorphous precursor densification to transparent Nd:Y2O3 Ceramics

Abstract

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 2at.% Nd3+ doped Y2O3 was synthesized by gelation of sol of yttrium and neodymium nitrates with l-alanine at 80°C for 16h followed by gel combustion in microwave. A part of microwave precursor was heat treated at 700°C for 5h 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 17–19nm by TEM. Another part of microwave precursor on calcination at 1000°C for 3h led to formation of fully crystalline Nd:Y2O3 with particles in size range of 35–85nm. Both partially crystalline amorphous precursor and fully crystalline Nd:Y2O3 were compacted at 400MPa by cold isostatic press and sintered at 1750°C for 10h under vacuum (10−5mbar). The partially crystalline Nd:Y2O3 amorphous precursor densified to 99% with 65% transmission at 2500nm (0.5mm 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 ≤2μm 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.