Deformation during nanoindentation in highly oriented nonlinear optical Ba2TiGe crystalline layers at glass surface

Transcription

1 FFAG4, 2008, Nagahama Deformation during nanoindentation in highly oriented nonlinear optical Ba2TiGe TiGe2O8 crystalline layers at glass surface Including deformation behaviors in nanocrystallized glasses 1. Background and motivation 2. Deformation during nanoindentation T.Komatsu and F.Torres Nagaoka University of Technology, Japan

2 Glass Key materials in Information Technology Glass Structure: Inversion Symmetry No second-order optical nonlinearity No ferroelectric properties Crystallization of ferroelectric/nonlinear optical crystals

3 Crystallization of Glass Nanocrystals Highly oriented crystals Single crystals Nanocrystallized glass fibers fibers Surface crystallized glass Laser-induced crystal patterning

4 Transparent nanocrystallized glass Nanocrystals: 10~20 nm Light wave conversion SHG

5 Highly oriented crystallized glass BaO-TiO TiO2-GeO2 glasses Ba2TiGe TiGe2O8 crystal d:~20 pm/v Heat-treated 760 o C, 1h Crystalline layer

6 Laser-induced crystal patterning 1. Rare-earth atom heat processing 2. Transition metal atom heat processing 6 F 9/2 (~1064 nm) 1064 nm SHG Crystal Sm 3+ Dy µm 6 H 5/2 6 H 15/2 Glass

7 New advanced crystallized glasses!! Elastic/mechanical behaviors?

8 Example #1 Transparent nanocrystallized glasses ses Example #2 25K2O-25Nb2O5-50GeO2 15K2O-15Nb2O5-70TeO2 Transparent surface crystallized glasses 40BaO-20TiO2-40GeO2 Are there any new features and concepts in deformation behaviors?

9 Vickers Nanoindentation Apparatus: Akashi MZT-4 Test standards: ISO Correlations: Initial penetration, Instrument compliances µ Martens hardness MH = P max h 2 max Young s s modulus Elastic recovery

10 Cube resonance method 3x3x3 mm 3 Longitudinal/shear sound velocities Young s s modulus, Debye temperature, etc

11 Example #1 GeO2-based nanocrystallized glasses 25K2O-25Nb2O5-50GeO2: Tg=622 o C, Tx=668 o CT Nanocrystals 10~30 nm: K3.8Nb5Ge3O20.4 Transmittance (%) As-quenched 680,1h 720,1h 850,1h Wavelength (nm) 720 o C, 1 h Excellent optical transparency!!

12 f: Volume fraction of nanocrystals 630 o C, 1 h: f= o C, 1 h: f= Density (g/cm 3 ) Tx=668 o C Tg=622 o C Heat-treatment temperature ( o C)

13 Usual Vickers hardness: large scale deformation Load: 490 mn, Loading time: 10 s, in air (RH=54%) Vickers hardness (GPa) f=0.32 f=0.60 Tx=668 o C Tg=622 o C f= Heat-treatment temperature Percolation? ( o C) Largely improved due to the nanocrystallization

14 Vickers nanoindentation Load (mn) Load/unload speed : 10 mn/s, in air (RH=54%) Nanocrystallized glass C,1h f= Displacement (µm) at hmax=1.0 µm MH=3.63 GPa E=78.3 Gpa (E=85.5 GPa) ER=46% Glass: MH=3.09 GPa, E=64.7 GPa, ER=49%

15 Martens hardness Martens hardness(gpa) Glass Base glass Nanocrystallized glass(630 C) Nanocrystallized glass(720 C) Nanocrystallized glass Displacement (µm) f=0.32 f=0.60 Largely improved!!

16 Vickers nanoindentation hmax: : 0.6 µm 4.1 Martens hardness (GPa) Tg=622 o C f=0.32 f=0.60 Tx=668 o C f=0.8 Very sensitive for the formation of nanocrystals Heat-treatment temperature ( o C) The composite of nanocrystals and the glassy phase has a strong resistance against deformation

17 Elastic and mechanical properties of the base glass and transparent nanocrystallized glasses in the KNbGeO 5 system Properties glass Nano- crystallized (630 o C,1 h) Nano- crystallized (720 o C,1 h) Density (g/cm 3 ), d Refractive index at nm, n Molar volume (cm 3 /mol), V m Poisson ratio, n Shear modulus (GPa), G Bulk modulus (GPa), K Young s s modulus (GPa), E Debye temperature (K), q D Fractal bond connectivity, F d

18 630 o C, 1 h f=0.32 Can you see connections of nanocrystals?

19 15K2O-15Nb2O5-70TeO2 K C = E 1/ 2 P 0.018( ) ( 3 / 2 H C ) K C = 2Eγ 1 ν f 2 Fragile glass nanocrystallization Elastic/mechanical properties are largely improved. Fracture surface energy: γf 0.5 J/m J/m 2

20 Example #2 Highly oriented nonlinear optical Ba2TiGe TiGe2O8 crystalline layers at glass surface Glass: 40BaO-20TiO2-40GeO2, T g =664 o C, T x =770 o C Heat-treated: treated: at 670, 700, 720, 750 o C, for 3 h c-axis-oriented Ba2TiGe2O8 crystals c-axis

21 Surface Crystalline layers: 7~10 µm Intensity (arb. unit ) Ba2TiGe2O8 crystalline layer (001) Glass (311) (002) 750 o C, 3h Ba2TiGe2O8 crystals 670 o C, 3h θ (deg)

22 Indentation direction Normal 7-10 m Crystallized Surface Lateral 22

23 Base glass: Normal direction MH=5.2 GPa at h max =0.5 µm, ER=49 % Load (mn) Base Glass 0.25 µm/s in air, RH=54% Displacement (µm)

24 Surface Crystallized Glass: 670 o C Load (mn) Penetration rate 5 µm/s Normal 20 nm 0.25 µm/s Sliding Load (mn) µm ER = 70% Displacement (µm) Displacement (µm) P=40 mn for h=0.5 µm Glass: P=300 mn for h=0.5 µm Crystalline layers deform very easily

25 Surface Crystallized Glass: 750 o C 50 Load (mn) µm/s ER=62 % Sliding 5 µm/s Displacement (µm)

26 Surface crystalline layers: 7~10 µm Martens Hardness (GPa) : 750 o C : 720 o C : 670 o C Large deformation Large elastic recovery Penetration depth (µm) Base glass: MH=5.2 GPa at h max =0.5 mm H v =4.2 GPa at 490 mn

27 Surface crystallized glass: 700 o C Penetration rate 0.25 µm/s Load (mn) Lateral direction Displacement (µm)

28 Normal Elastic recovery is important!! Vickers indenter Displacement Loading Unloading Ba 2 TiGe 2 O 8 crystal Normal Plastic deformation is important!! Lateral Lateral

29 Summary Transparent nanocrystallized glasses 25K2O-25Nb2O5-50GeO2 Elastic/mechanical properties change rapidly at the volume fraction of nanocrystals ~35% 15K2O-15Nb2O5-70TeO2 Fracture toughness is largely improved by nanocrystallization Transparent surface crystallized glasses 40BaO-20TiO2-40GeO2 rain-oriented Ba2TiGe2O8 crystals show poor mechanical properties and different elastic behaviors at micro- and nano levels