After a lot of trial and error, we determined that this recipe yields the highest quality samples.
1. Dissolve terbium nitrate in 7.8 mL deionized water.
2. Add 4.00 mL TMOS (tetramethylorthosilicate, 99%)
3. Magnetically stir solution for 10 minutes
4. Ultrasonically stir solution for 10 minutes
5. Add 20 μL concentrated nitric acid
6. Magnetically stir solution for 1 minute
7. Ultrasonically stir solution for 1 minute
8. Put sol into 4 tightly capped polystyrene disposable test tubes
Aging/Drying
9. Gel at room temperature for 72 hours
10. Ramp at 5ēC/hr to 60ēC
11. Add 1mL deionized water to each test tube (check about an hour before they reach 60ēC, and add water as soon as they start to gel)
12. Sit at 60ēC for 48 hours
13. Ramp at 5ēC/hr to 90ēC
14. Remove caps
15. Sit at 90ēC for 48 hours
16. Ramp at 2ēC/hr to 110ēC, then sit for 48 hours
17. Let cool to room temperature
Annealing
18. Heat samples to 900ēC at 1ēC/minute
19. Dwell here if desired
20. Turn off heat
21. Remove samples when oven gets down to ~500ēC to cool in air
22. After 5-10 minutes, samples are ready to go!