Kosyanov D. Formation and structural-phase state of 1-4 at. % Nd3+:Y3Al5O12 laser nanoceramics

Thesis is devoted to revealing regularities of phase- and structure formation, densification of 3-хY2O3-хNd2O3-5Al2O3 (х=0.03-0.12) oxide powders during reactive sintering of Y3Al5O12:Nd3+, as well as to determination of formation conditions of Y3Al5O12:Nd3+ (1-4 аt. %) laser nanoceramics. An optimized synthesis temperature range of Y3Al5O12:Nd3+ phase formation (1200-1500 °С) at the reactive sintering of starting oxide powders is achieved in the powder systems with the following characteristics: D(Аl2О3)~250 nm, disproportion parameter of particles R (D(Аl2О3)/D(Y2О3,Nd2О3))~2.5 and 5. It has been shown that minimization of closed porosity value on the whole solid-state synthesis trajectory of garnet phase (1500 °С) promotes stabilization of microstructure of compacts, which was realized for R~2.5 powder system. Nd3+ -> Y3+ isomorphous substitution in the garnet structure (Y1-xNdx)3Al5О12 (x=0.01-0.04) for powder system with R~2.5 has a threshold nature (starting from 1350 °С) with interaction between monoaluminates (Y1-yNdy)AlO3, (Nd1-zYz)AlO3 (y,z<=0.02) and alumina at 1200-1500 °С temperature range as a dominant mechanism. Segregation of zirconium ions along grain boundaries of Y3Al5O12:Nd3+ nanoceramics sintered at 1750 °С promotes stabilization of the average grain size of 10 mkm at a concentration of residual porosity П<10-2 vol %. Laser-quality Y3Al5О12:Nd3+ (1-4 at. %) nanoceramic have been obtained with the relative density =>99.998 % and optical losses <=10-1 cm-1 (lambda=1.064 mkm), which are equal to those of corresponding YAG single crystals.