amorphous materials at high pressure
DESCRIPTION
Amorphous materials at high pressure. Chrystèle Sanloup. CSEC, University of Edinburgh, UK Université Pierre et Marie Curie Institut de Physique du Globe de Paris, France. High pressure amorphs - Synthesis. ▪ Pressure-induced amorphization (PIA). ▪ Amorphous-amorphous transitions (AAT). - PowerPoint PPT PresentationTRANSCRIPT
Amorphous materialsAmorphous materials at high pressure at high pressure
Chrystèle Sanloup
CSEC, University of Edinburgh, UKCSEC, University of Edinburgh, UKUniversité Pierre et Marie CurieUniversité Pierre et Marie Curie
Institut de Physique du Globe de Paris, France Institut de Physique du Globe de Paris, France
Not thermodynamically stable state choose appropriate -P-T paths
N.B.: confusion or identification of amorphous forms and quenched liquids (glasses) cf. example of S upon decompression
High pressure amorphs - SynthesisHigh pressure amorphs - Synthesis
▪ Pressure-induced amorphization (PIA) ▪ Amorphous-amorphous transitions (AAT)
▪ Opal (amorphous SiO2) - SEM image
Basic unit = nanoscale grains short-order range
Electron microscopy: Best characterization of amorphous materials but not available at HP, and can high-pressure amorphs be quenched ?
Amorphous materialsAmorphous materials
Gaillou et al., Am. Min. 2008
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
I- Loss of long-range order Diffuse scattering (X-rays and neutrons)
! Except for heavy elements, X-ray criteria for PIA=disappearance of peaks(misleading)
Fujii et al. JPC:SSP 1985 Luo et al. PRB 1993SnI4Sulfur
Structure unrelated to that of the liquid phase at P0
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
a-CO2
Santoro et al., Nature 2006.
Gregoryanz et al., JCP 2007.
a-N
I- Diffuse X-ray scattering:
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
Sanloup et al., PRL 2008
amorphous Sulfur
! Very high background/signal ratio
I- Diffuse X-ray scattering:
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
I- Diffuse X-ray scattering:
Boehler-Almax anvils
▪ Problems at high P: 1- limited Q-range 2- background substraction
- Empty cell pattern- Crystalline pattern
▪ Advantages of low T: homogeneous samples
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
II- Density/volumetric measurements
Deplacement of a piston in a cylinderEx: PIA of ice Mishima Nature 1984
Large volume decrease: ~20%
-PIA large volume reduction importance of density measurements on am.
Isample = I0 ∙exp(−diadiatdia−samplesampletsample)
3 unknowns need 3 equations/measurements measurements up to 60 GPa
Sato & Funamori, Rev. Sci. Instr. 2008.
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
II- Density/volumetric measurements - Radiographic techniques
Liu et al, PNAS 2008.
Up to 10 GPaSe: heavy element
Kaplow et al., Phys. Rev. 1965.
)()()( QIQIQI incohsampcoh 1)(lim QSQ
max
0
)sin(1)(2
1)(4)(Q
drQrQSQrgrrF
, normalization factor such as
Access to:-: initial slope- local structure
2)(
)()(
Qf
QIQS coh
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
II- Density measurements - X-ray diffraction technique
Characteristics of HP amorphsCharacteristics of HP amorphs
▪ Crystal-like properties: local structure
H2O
Strongly peaked diffraction patterns
Sulfur
-ZrW2O8 amorphous
Keen et al. PRL 2007
IINS (inelastic incoherent neutron scattering)
Similarity of LDA and Ice Ih
Tse Nature 1999
Characteristics of HP amorphsCharacteristics of HP amorphs
▪ Crystal-like properties: phonon density of states
Characteristics of HP amorphsCharacteristics of HP amorphs
▪ Crystal-like properties: density
Daisenberg et al., PRB 2007.
Compressibility similar to that of the crystalline counter-part
Sulfur
Silicon
a-CO2
Simple molecular systems: COSimple molecular systems: CO22, N, N22
High T: molecular to non-molecular transition high-energy barrier
Low T: molecular crystal to amorphous form transition
a-N
Gregoryanz et al. PRB 2001, JCP 2007
Goncharov et al. PRL 2000
Santoro et al., Nature 2006.
a-CO2
Santoro et al., Nature 2006.
a-CO2
↑P: PIA, CO2-VI like a-CO2
↓P: AAT, CO2-V like→ CO2-III like a-CO2
↓P: re-crystallization into CO2-I
▪ Amorphous-amorphous transition:
Simple molecular systems: COSimple molecular systems: CO22, N, N22
VI
Simple molecular systems: SSimple molecular systems: S88
631521
112
611
Recrystallisation: a-S → S-III
PIA is the precursor of the phase transition to the high-P polymorph
CN=15.0+/-0.4
CN=16.1+/-0.1
AAT in conjunction with S-III → S-IV transition, rather 1st order transition
Simple molecular systems: SSimple molecular systems: S88
Large volume collapse upon PIA
AAT : Low-density amorph (LDA) High-density amorph (HDA)
Simple molecular systems: SSimple molecular systems: S88
▪ AAT upon decompression:
2nd order transition: LDA → liquid-like a-S
Re-crystallization at 0.25 GPa-room T into S-I
Simple molecular systems: SSimple molecular systems: S88
▪ Crossing of the metastable extension of the melting line
Cold Cold vsvs mechanical melting mechanical melting
Mishima et al., Nature 1984.
PIA
Tse et al., Nature 1999.Mishima, Nature 1996.
Case of H2O
Hemley et al., Nature 1988.
▪ Crossing of the metastable extension of the melting line
Cold Cold vsvs mechanical melting mechanical melting
Case of SiO2
Crystalline structures collapse regardless of their melting behavior
Amorphization systematically connected with crystal-crystal transformation just above the
amorphisation T.
Brazhkin et al. JNCS 1997
Cold Cold vsvs mechanical melting mechanical melting
▪ Arguing for mechanical melting: elastic instabilities evidenced before PIA
Phonon softening in Ice Ih PIA predicted at 2.5 GPa
Cold Cold vsvs mechanical melting mechanical melting
Violation of Born criteria
Gregoryanz et al. PRL 2000
Case of SiO2
Strässle et al. PRL 2004
Case of H2O
NB: P of PIA by mechanical melting always overestimated by Born criteria
B3=(C11-C12)∙C44-2C142
S-I 16 GPa – 175 K S-I 41 GPa – 175 K (just before amorphization)
Role of defectsRole of defects
▪ Defective X-ray patterns upon approaching PIA
Case of sulfur
▪ P-induced reduction of Nb2O5 : Simultaneous amorphization at 19 GPa-300K Reduction O defects in the lattice
▪ Numerical simulations:- defect-free: no transformation until mechanical limit is reached- sample with one vacancy: transformation starts at lower P
G’=(C11-C12)/2-P
Role of defectsRole of defects
Serghiou et al., PRL 1992.
Defects can destabilize the lattice at pressures much lower than the instability pressure.
Bustingorry and Jagla, PRB 2005.
ConclusionsConclusions
▪ PIA occurs if a parent phase is compressed beyond its thermodynamic stability field
▪ Occurs generally at low T: lack of thermal energy not enough atomic mobility for the crystalline-crystalline transition to occur
▪ PIA is the precursor of the phase transition to the high-P polymorph high-P amorphs have crystal-like properties (distinct from glasses)
▪ PIA is accompanied by a large volume reduction
▪ a large variety of materials transform into amorphs at high P
▪ high-P amorphs may undergo 1st or 2nd order AAT
▪ high-P amorphs are often difficult to recover at ambient conditions
▪ Industry of polymers: improved kinetic stability, enhanced mechanical properties
Yu et al., APL, 2009
ConclusionsConclusions
▪ Use of high P to synthesize high quality quenched amorphs
Ivashchenko et al. PRB 2007
Nanocrystalline Siparticle size: 2.2 nm
Nanocrystalline S-III X-ray amorphous: If particle size ~ 10 Å
i.e. ~ 3 crystallographic cells
Scherrer equation:
Particle size=K
w1/2 cos(
Bustingorry and Jagla PRB 2005
Platelets of the high-P phase nucleate on the vacancyBut growth inhibited very small crystal size
a-S 54 GPa
Crystalline S-III
Nanocrystalline S-III?
X-ray amorphs or nanocrystallites ?X-ray amorphs or nanocrystallites ?
LDA and HDA forms have cristalline-like properties (except for complex H2O).
HDA (water) can not be assimilated to a supercooled liquid,Neither LDA/HDA transition to a 2-state liquids (i.e. liquid-liquid transition)by way of csqce
Tse:
Differences between high P amorph and glasses
Amorph-amorph transitionsAmorph-amorph transitions
First evidenced in aSi and a-Ge? (Shimomura Philos Mag 1974 29 p547?),AAT tend to be 1st order transitions (Si, S, H2O?)
confusion or identification of amorphous forms and quenched liquids (glasses) cf. example of S upon decompression
Mishima et al., Nature 1985
2- T increase: High-density amorphous ice (HDA)→Low-density amorphous ice (LDA)
1- Pressure-induced amorphization
3- P increase:LDA→HDA
LDAHDA
Amorphous-amorphous transitionsAmorphous-amorphous transitions
Case of H2O
Klotz et al., PRL 2005
Neutron diffraction data (see D>>)But different picture given by X-rays (see O>>)
N.B.: very complex H2O phase diagram!!!
▪ HDA water: - continuous structural changes towards close-packing - may re-crystallize into different phases
Amorph-amorph transitionsAmorph-amorph transitions
▪ HDA-LDA: 1st order transition ?
Boehler-Almax anvils
430 1010)(lim
T
BQ K
TkQS
Additional constraint at very high pressures:
Negligeable on the expal pattern
• Pb 2: the higher the pressure, the more difficult it is to get the background properly
• Pb 1: limited Q-range:
Amorphous sulphurAmorphous sulphur
Tse Nature 1999
Liquid water
Amorphous HDA
Add P-T phase diagram(cf Klotz)Add PIA paths
Strassle PRL 2007
Cold Cold vsvs mechanical melting mechanical melting
Case of simple molecular systems:Systematic PIA from molecular to non molecular at low T (not at high T)Recovery of the amorph down to low P (N, Eremets, us with S)
Case of tetraedrally coordinated systems (classical case)
Case of Si, Ge, III-IV compounds and their solid solutions, etc Tsuji et al., Brazhkin et al.: PIA upon DECOMPRESSION from METALLIC state.
Tsuji JNCS 1996
1- Semi-conductor zincblende structure
2- Incr.P: metallic -tin structure
3- decr.P: amorphization, T-dependant
Meade and Jeanloz, PRB 1987
Cr-emulsion mask (1mm lines) on a SiO2-glass
Hemley et al., Nature 1988
Amorphization is thermodynamically induced
But glass not amorphous silica !
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
Differences between high P amorph and glasses
Deb et al., Nature 414, 528 (2001)
Pressure-induced amorphization of Si (porous Si)
Decompression: HDA→LDA transition(Raman spectroscopy)
Check that the LDA curve goes on the HAD(which then coincides with Si-V)
How was LDA formed? Real PIA or Si gel?
Daisenberg et al., PRB 2007
Transition predicted at 13.7 GPa,Between 14 and 16 GPa experimentally
Brazhkin et al. JNCS 1997
Ultrasonic measurements
Arguing for mechanical melting: elastic instabilities evidenced before PIA
Phonon softening in Ice IhSträssle et al. PRL 2004
PIA predicted at 2.5 GPa
Cold Cold vsvs mechanical melting mechanical melting
Case of H2O
Brief statement on Born criteria
high P amorphs have cristalline-like properties (cf Tse PRB 2005 et aS).
- Similar thermal conductivity (H2O, Johari PRB2004)
- memory of the initial crystallographic orientation or anisotropy of the amorph: single crystal → amorph (incr.P) → single crystal (decr. P) with same orientation (cf AlPO4, Kruger and Jeanloz 1990 or Brillouin scattering on AlPO4 by Polian PRL1993 and a-SiO2 by McNeil PRL1992)
Characteristics of HP amorphsCharacteristics of HP amorphs
Case of simple molecular systems:Systematic PIA from molecular to non molecular at low T (not at high T)Recovery of the amorph down to low P (N, Eremets, us with S)
Case of tetraedrally coordinated systems (classical case)
Case of Si, Ge, III-IV compounds and their solid solutions, etc Tsuji et al., Brazhkin et al.: PIA upon DECOMPRESSION from METALLIC state.But also case of S (cf Wilson, from trigonal state, in the Z. Crist. Paper?)
Tsuji: There are two methodsto obtain amorphous materials using high pressure.One is amorphization above the thermodynamic transitionpressure Pt, [1,2] and the other is amorphizationfrom the quenched high-pressure phase below Pt
High pressure amorphsHigh pressure amorphs
-Interests: synthesis of new materials (properties?), In particular through high P polyamorphism
Amorphous (industrial interests?)
-Theoretical interests:- discussion of polyamorphic transitions, 1st vs 2nd order- amorphs taken as proxies for liquids and the search for 2nd critical points- mechanisms of PIA?
High pressure amorphs - InterestsHigh pressure amorphs - Interests
Characterizaton of amorphs at high PCharacterizaton of amorphs at high P
II- Density/volumetric measurements
Strain/gauge technique: limited to <10 GPa but very high precision (0.15%)
Brazhkin et al., JETP 89, 244 (2009)
Tsiok et al., HPR 10, 523 (1992)
g(r)
r
1
0
• I(2) S(Q), structure factor
• S(Q) g(r), radial distribution fonction
sin4
exp)(
2)(
20
QdQfAI
IQS
dQrQQSQnr
rg sin12
11)(
02
with
Amorphous materialsAmorphous materials
▪ No long-range order diffuse X-ray scattering