Effect of SiO2 on Densification and Microstructure Development in Nd:YAG Transparent Ceramics

Abstract

This paper examines the influence of SiO2 doping on densification and microstructure evolution in Nd3xY3−3xAl5O12 (Nd:YAG) ceramics. Nd:YAG powders were doped with 0.035–0.28 wt% SiO2 and vacuum sintered between 1484° and 1750°C. 29Si magic‐angle spinning nuclear magnetic resonance showed that Si4+ substitutes onto tetrahedrally coordinated Al3+ sites. High‐resolution transmission electron microscopy showed no grain boundary second phases for all silica levels in samples sintered at 1600°–1750°C. Coarsening was limited by a solute drag mechanism as suggested by cubic grain growth kinetics and transmission electron microscopy energy‐dispersive X‐ray spectroscopy observations of increased Nd3+ concentration near grain boundaries. Increasing SiO2 content increased both densification and grain growth rate and led to increasingly coarsening‐dominated sintering trajectories. Fine‐grained (<3 μm), highly transparent (>82% real in‐line transmission) ceramics were produced by sintering 0.035 wt% SiO2‐doped ceramics at 1750°C for 8 h. Coarse‐grained (18 μm), transparent samples were obtained with 0.28 wt% SiO2‐doped Nd:YAG when sintered at 1600°C for 8 h.

Towards Bright and Fast Lu3Al5O12:Ce,Mg Optical Ceramics Scintillators

“…[ 18,19 ] However, differently from the laser process, which involves localized excitations, carrier migration to the luminescent centers during the scintillation process could be severely delayed by point defects induced by sintering agents. As a result, the commonly used simultaneous introduction of sintering agents like (C 2 H 5 O) 4 Si (tetraethyl ortho-silicate, TEOS) and MgO in laser ceramics induces a transparency improvement accompanied unfortunately by a deterioration of the scintillation properties.…”

Microstructure evolution of SiO2, ZrO2-doped Y3Al5O12:Nd3+ ceramics obtained by reactive sintering

“…Assuming that all Si 4+ and Zr 4+ ions in an overall concentration of 0.24 wt% substitute for aluminum cations, we will have approximately 0.3 at% Al 3+ ion excess over the stoichiometric composition [25]. Patel et al demonstrated that Al 3+ cations excess up to 0.2 mol% may be compensated via formation of antisite defects in garnet structure [46].…”

“…Since the first report on lasing using YAG:Nd 3+ ceramic gain media [18], many research teams were involved in development of optical ceramics with improved laser characteristics, studying sintering routes, nanopowders synthesis and consolidation techniques [19], as well as establishing the role of sintering additives in order to control the diffusional mass transport [20]. In [21][22][23][24][25] the effect of silica on densification of garnet ceramics was studied. It has been determined that doping by SiO 2 would not be an appropriate approach to obtain the extremely low level of residual defects necessary for high-energy lasers [14].…”

Fabrication of Yb3+-doped YAG transparent ceramics by aqueous gelcasting

“…To obtain Yb:YAG transparent ceramics with desired microstructure, its fabrication technology is very important. In recent years, many efforts have been made on YAG-based ceramics related to the synthesis of high-purity and agglomeration-free powders [8][9][10], amount and choice of sintering additives [11][12][13], optimization of sintering process [14][15][16], post-treatment [17][18][19][20], etc. Powder shaping technology was also important for obtaining highly transparent ceramics.…”