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, YM₂O₃ 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 1064nm 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.