Microstructure and optical properties of Er2O3 - Doped potassium sodium niobate-tellurite glass-ceramics

In this work, transparent glasses of erbium oxide (Er₂O₃)-doped KNN-tellurite were successfully prepared by using the incorporation method. Experiments started with the preparation of KNN powder by simple mixed oxide method using calcination temperature of 900°C for 5 h. Then, the calcined KNN powder was mixed with TeO₂ and 0.5-1 mol% Er₂O₃ dopant. Each batch was subsequently melted at 800oC for 15 min in a platinum crucible using an electric furnace. The quenched glasses were then subjected to heat treatment at various temperatures for 4 h in order to form glass-ceramics with the desired crystal phases. XRD results showed that KNN solid solution distributed over the glass-ceramic samples. Scanning electron microscopy SEM revealed that nano-crystals of KNN and some secondary crystals precipitated in the glass-ceramics. Crystal sizes increased with increasing heat treatment temperatures. The optical and physical properties of the prepared glass-ceramics were measured. The values of refractive index ranged between 1.99 and 2.15, while that of density ranged between 4.64-5.18 g/cm³. Energy band gap from the transmission cut-off wavelength (Eg) was measured as 2.89-3.20 eV.