Serena Di Nunzio Paola Palmero

1. Chlorides- and nitrates-derived YAG powders: differences on phases evolution and powder sinterability Serena Di Nunzio Paola Palmero VI Convegno INSTM - Perugia

2. Introduction • YAG: Yttrium Aluminium Garnet – Y3Al5O12 Other Y-Al phases: • YAM – Monoclinic Y4Al2O9 • YAP – Perovskite YAlO3 • Cubic YAlO3 • h-YAlO3 – hexagonal (metastable phase) • Properties: transparency, high creep resistance • Applications: alumina-based composites, optical devices (laser host materials) Nano-structured YAG powders VI Convegno INSTM - Perugia

3. Extra-ammonia solution H2O pH-metre pH 9 ammonia solution EtOH Oven-drying Syntheses: Reverse-strike co-precipitation Chlorides solution Nitrates solution Chlorides: 4 cycles Nitrates: 1 cycle Chlorides: 2 cycles Nitrates: 1 cycle VI Convegno INSTM - Perugia

4. DSC/TG DSC and TG analyses of as-synthesized Chlorides-Powderand Nitrates-Powder 890°C 995°C 930°C 1020°C h-YAlO3 YAG VI Convegno INSTM - Perugia

5. As-dried 10 20 30 40 50 60 70 Y 2 q (Degree) Y Y Y Y Y Y Y Y Y As-dried 10 20 30 40 50 60 70 2 q (Degree) XRD: phases evolution at low temperatures for short treatment time Chlorides-Powder Nitrates-Powder 700°C 600°C 500°C 450°C YAG crystallization yet from 500°C Amorphous up to 700°C VI Convegno INSTM - Perugia

6. Y Y h Y Y Y Y h h Y Y Y Y h Y h Y Y h Y Y Y Y Y h Y Y Y Y Y h Y Y Y Y Y Y h Y Y h h Y Y h Y Y Y Y Y Y Y Y Y Y Y Y Y h Y Y h Y h Y Y 10 10 20 20 30 30 40 40 50 50 60 60 70 70 2 q (Degree) 2 q (Degree) Y XRD: phases evolution at medium temperatures for short treatment time Chlorides-Powder Nitrates-Powder 900°C 800°C Hexagonal YAlO3 from 800°C Only YAG crystallization VI Convegno INSTM - Perugia

7. Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y 10 20 30 40 50 60 70 2q (Degree) XRD: phases evolution at medium-high temperatures for short treatment time 1350°C VI Convegno INSTM - Perugia

8. 160 140 120 100 Crystallite size (nm) 80 60 40 20 0 0 500 1000 1500 T (°C) TEM VI Convegno INSTM - Perugia

9. Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y h h h h Y Y Y Y Y Y 10 20 30 40 50 60 70 Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y 2 q (Degree) Y Y Y Y 10 20 30 40 50 60 70 2 q (Degree) XRD: phases evolution at 800°C in function of treatment time 48 hrs 24 hrs 5 hrs 4 hrs 2 hrs 1 hr 0.5 hr 0 hr VI Convegno INSTM - Perugia

10. 14000 12000 10000 8000 6000 XRD Peak Intensity (counts) 4000 2000 0 0 10 20 30 40 50 time (h) XRD: phases evolution at 800°C as a function of treatment time <420>YAG <120> h-YAlO3 YAG Nitrates Chlorides h-YAlO3 VI Convegno INSTM - Perugia

11. 10 20 30 40 50 60 70 2 Theta (degrees) Sinterability of TT30’@800°C Uniaxial pressing 300 MPa Abrupt shrinkage at about 850°C due to crystallization phenomena VI Convegno INSTM - Perugia

12. 48h V/g DSC normalized signals m 10 24h EXO 800 900 1000 1100 1200 As dried T (°C) 25 30 35 40 2q (Degree) Sinterability of TT24h and 48h @800°C VI Convegno INSTM - Perugia

13. 0.00 10°C/min @ 1500°C -0.02 ) 3h @ 1500°C 0 L/L 10°C/min @ Ta D -0.04 Linear shrinkage ( -0.06 -0.08 0 200 400 600 800 1000 1200 1400 Temperature (°C) Sinterability of TT24h and 48h @800°C Green density: 46% theoretical value Fired density: 60% theoretical value 8% VI Convegno INSTM - Perugia

14. 0.00 ) 0 L/L D ( -0.05 -0.10 Linear shrinkage -0.15 -0.20 0 200 400 600 800 1000 1200 1400 Temperature (°C) Sinterability of TT48h @800°C and ball milled with Al2O3 spheres 18% Green density: 46% theoretical value Fired density: 86% theoretical value VI Convegno INSTM - Perugia

15. Conclusions Reverse-strike co-precipitation is effective to obtain PURE YAG NANOMETRIC POWDERS Starting precursors (Chlorides or Nitrates) affect the PHASES EVOLUTION during heating treatments Preliminary sintering test allowed to obtain fine-grained homogeneous structure and basic information in view of SPS optimization VI Convegno INSTM - Perugia

16. Thanks! VI Convegno INSTM - Perugia