Fabrication of Nd:YAG transparent ceramics with TEOS, MgO and compound additives as sintering aids

1 at.% Nd:YAG transparent ceramics were fabricated by solid-state reaction and vacuum sintering method using commercial Al2O3, Y2O3 and Nd2O3 as raw materials, TEOS, MgO and TEOS combined with MgO were used as additives. When using TEOS or MgO as sintering aids separately, the optimum dosage is 0.5 and 0.2 wt%, respectively. But residual second phases in the grain boundaries and pores are easily generated by adding excessive TEOS or MgO. The maximum transmittance at 1064 nm of the sintered Nd:YAG ceramics is doped 0.4 wt% TEOS combined with 0.08 wt% MgO, nearly pore-free microstructure with the average grain size of more than 30 μm was obtained in this highest transparent sample. All samples sinter to near full density (>99.8%) at 1700 °C and the sample with 0.4 wt% TEOS combined with 0.08 wt% MgO has the highest densification rate. The excellent feature of using compound additives is to make the intensified liquid sintering start at a lower temperature in vacuum sintering, promoting the densification rate and obtaining the uncontaminated crystalline grains.