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TA+PXRD coursePart 5, HTXRD, our tool and examples
November 2017, Mikko Heikkilä
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 114.11.2017 www.helsinki.fi/yliopisto
High temperature XRD – overview
HTXRD In general• In the early history the main application was high temperature
phase changes
• equipment were developed later for low temperatures and
applications for in situ, time-resolved and in operando studies
• In in situ experiments a system or a material is studied at non-ambient
conditions where chemical or physical processes occur
• In operando requires the system studied to be under identical conditions
as in, for example, an industrial process
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 214.11.2017
www.helsinki.fi/yliopisto
HTXRD – overview
Why not ex situ, where• Sample mounting is simple (and usually somewhat standardized)
• Samples can be taken from various stages of materials processing
and analyzed in detail
• Complementary studies (optical microscopy, SEM, TEM, elemental
analysis, etc.) can be carried out
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 314.11.2017 www.helsinki.fi/yliopisto
HTXRD – overview
In situ enables one to• learn something about how materials are made, how they behave
during heating and how they might change in an application
• make an easier choice for the appropriate temperatures for post
deposition heat treatments and ex situ complementary
• without in situ data, one would need numerous heat treated samples
and/or lot of guesswork to figure out the useful temperatures
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 414.11.2017
www.helsinki.fi/yliopisto
HTXRD – overview
Typical experiments:• Dynamic powder diffraction: time-resolved experiments are
performed to follow materials during chemical or physical reactions
and processes
• Static experiments: information about materials under steady-state
conditions in a complex system is obtained, e.g. catalysts in a
reactor at operating conditions, or isothermal oxidation/reduction of
the sample in different atmospheres
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 514.11.2017 www.helsinki.fi/yliopisto
HTXRD – overview
Measurement examples• Time-resolved studies:
• materials synthesis (solid state, sol/gel, hydrothermal, thin film growth,…)
• cathode and anode materials in lithium batteries during charge/discharge
cycles
• adsorption/desorption, ion exchange and intercalation reactions of
layered or microporous materials
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 614.11.2017
www.helsinki.fi/yliopisto
HTXRD – overview
Measurement examples• catalysts under operating conditions, hydrogen storage materials
during uptake and release of hydrogen or studies of electrochemical
reactions
• materials during physical processes or interactions, e.g.
piezoelectric materials in oscillating electrical fields, studies of
strain/stress development during mechanic treatment of metals or
reaction to changes in an external magnetic field.
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 714.11.2017 www.helsinki.fi/yliopisto
HTXRD in short
Non-ambient conditions allows one to see
• Phase transitions
• either reversible or irreversible
• Oxidation/reduction of the sample
• Usually irreversible, unless atmosphere is changed during the
measurement
• Reaction temperatures and products of mixtures
• Irreversible, unless reaction product has a different low temperature
phaseTA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 814.11.2017
www.helsinki.fi/yliopisto
HTXRD in short
Non-ambient conditions allows one to see
• Crystallization of amorphous samples
• Thin films deposited at low temperatures are often amorphous and
sometimes require crystallization
• Determination of thermal expansion parameters
• Since XRD is highly sensitive to unit cell size, determining the size as a
function of temperature is usually quite straightforward
• Unlike with dilatometry, XRD allows one to evaluate anisotropic expansion
along different cell axes
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 914.11.2017 www.helsinki.fi/yliopisto
HTXRD – overview
Differences to ambient XRD• Atmosphere is something else
• Inert (N2)
• Oxidizing (air, O2)
• Reducing (H2, forming gas (mixture of H2 and N2))
• Moisture controlled
• Reactive if chamber allows for that
• Vacuum
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1014.11.2017
www.helsinki.fi/yliopisto
HTXRD
Different chambers• Few manufacturers, e.g. Anton-Paar and Edmund Bühler,
Bruker
• All look quite alike: x-ray transparent windows
in a big block of steel
• Walls kept at room temperature
with water circulation
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1114.11.2017 www.helsinki.fi/yliopisto
HTXRD
Different chambers• Heating either by
• direct heating (e.g. Pt strip) allows higher temperatures but less
control on thermal gradients
• heating coil surrounding the sample gives more even temperature
surrounding the sample
• Different atmosphere possibilities depending on the model
• Not very highly reactive gases, though
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1214.11.2017
www.helsinki.fi/yliopisto
HTXRD – Anton Paar
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1314.11.2017 www.helsinki.fi/yliopisto
HTXRD – Edmund Bühler
High and low temperature ovens• Left: HDK 1.4/2.4 temperature up to 1800/2400 °C
• Right: HDK S1, ambient temperature to 1600°C (standard) or
-185°C to + 400°C (with low temperature option)
• Direct heating in both
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1414.11.2017
www.helsinki.fi/yliopisto
HTXRD – Bruker
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1514.11.2017 www.helsinki.fi/yliopisto
HTXRD
Our tool• We have an Anton-Paar HTK1200N oven attached to our
PANalytical X’Pert Pro MPD diffractometer
• Both focusing and parallel beam optics work, angular range of the
GIXRD is slightly limited due to the oven design
• Temperatures from ambient to 1200 °C
• Currently available atmospheres include air, O2, N2,
forming gas (10 % H2 in N2) and vacuum (down to 10-4 mbar)
• Reducing atmospheres limited to ~700 °C and require oxidation of the
heating coils afterwardsTA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1614.11.2017
www.helsinki.fi/yliopisto
HTXRD
Our tool
TA+PXRD course - More HTXRDDecember 2015, Mikko Heikkilä 17
X-raywindows
Gas inlet
Gasoutlet
Vacuumline
Turbodragpump
Towardsbackingpump
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HTXRD in short
Restrictions when compared to ambient XRD• One can’t stay too long at each temperature if slow solid state
reactions are expected
• Since you never know, as short as possible measurements just in case
• Oven windows absorb 20–30 % of the radiation
• requires equally longer times per step
• Not always possible within short measurement time rule
→ angular range needs to be narrowed
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1814.11.2017
www.helsinki.fi/yliopisto
HTXRD in short
About measurement strategies• angular range should be as narrow as reasonably possible, in
order to make faster measurements with acceptable noise level
• Depends on possible phase changes or chemical reactions
• If material is known beforehand, educated guess can be made
by trying to guess the possible products and finding a suitable
range by comparing the reference cards
• Otherwise first a test measurent with wide range and larger T step
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 1914.11.2017 www.helsinki.fi/yliopisto
HTXRD in short
About measurement strategies• Step size and step time should be determined as instructed in
previous lessons, with the following obvious restrictions
• One should be even more strict on not to measure with too large step
size: definitely not more than seven points over FWHM
• Step time can’t be as long as total measurement time allows due to the
possible isothermal reactions
• IF one wants to determine precise profile of the peak with negligible
noise then it’s either back to RT for measurements, or synchrotron
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2014.11.2017
www.helsinki.fi/yliopisto
HTXRD in short
About measurement strategies• when the suitable angular range and other parameters are found,
then one of the following can be programmed
• constant temperature steps from RT to higher temperatures
• if temperature range of interest is known, then quick heating to
~50–100 °C below that temperature and with smaller steps to higher T
• larger steps until range of interest, then with smaller steps
• after the end temperature either cooling down to RT, or similar
ramp towards RT if reversible reactions need to be observedTA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2114.11.2017 www.helsinki.fi/yliopisto
HTXRD in short
About measurement strategies• Thin films (almost) always in GIXRD, powders in Bragg-Brentano
• With BB it’s possible to keep the detector in static mode, so that it
follows 3° range around certain angle and saves the intensity in
desired time intervals
• Allows one to heat constantly instead of temperature ramps
• However, poorly implemented in current Data Collector software
• BB also allows much faster measurements and therefore smaller
temperature steps (or larger angular range)TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2214.11.2017
www.helsinki.fi/yliopisto
HTXRD in short
Are the temperatures correct?• Calibration can be done using
• known phase transition temperatures (°C)
• e.g. KNO3 orth. → trig. 128
AgNO3 orth. → trig. 165
Ag2SO4 orth. → hex. 427
Quartz trig. → hex. (a → β) 573.0
• known thermal expansion of some substances (e.g. Si and/or Al2O3)
• better (and more difficult) approach, covers the whole temperature range
• Our device should be within ±10 °C error, probably betterTA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2314.11.2017 www.helsinki.fi/yliopisto
HTXRD in short
Are the temperatures correct?• K2SO4 measured with our oven
• Phase transition takes place around 580 °C while the literature
value is 587 °C
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2414.11.2017
www.helsinki.fi/yliopisto
HTXRD in short
Is the sample surface position correct?• Problem is that the surface position moves due to the thermal
expansion of the sample holder
• Although parallel beam is more or less unaffected by wrong
surface position, focusing geometry has a large angular
dependent shift due to wrong position
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2514.11.2017 www.helsinki.fi/yliopisto
HTXRD in short
Quite often the sample doesn’t remain the same
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2614.11.2017
Sample partlymelted
NH4NO3: new sample NH4NO3 after exposure to humid air
Clinkernew sample
Clinkerafter experiment
ZrO2 after heating to 1300 °C
Examples provided byChristian Resch(Anton Paar)
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HTXRD in short
How to deal with the wrong sample surface position?• There are ways to circumvent the sample holder issue
• Move the sample holder with the temperature
• Use internal standard that doesn’t react with the measured substance
• It’s thermal expansion should be known, then the surface position can be
corrected later using Rietveld method
• Possibility to correct the temperature as well
• Sadly no chance for this with coatings and thin films
• Both
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2714.11.2017 www.helsinki.fi/yliopisto
HTXRD examples
28Inorg. Chem. Seminar Seriers, Autumn edition 29.9.2010
Often data is presented either in• Three dimensions (left) or two dimensional intensity plot of the
same data(right)
• Pt sample, seems to remain at least partially metallic up to 1175 °C
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2814.11.2017
www.helsinki.fi/yliopisto
HTXRD examples
• as peak intensity should in general decrease as a function of 2q,
what happens at high angles? (tip: GIXRD measurement)
• some authors might state that
based on XRD data, the film is
highly (110) oriented
• please, don’t make this mistake
• in this case, (111) planes are
parallel to the surface
• could (and should) be verified with
q-2q measurement and a rocking curve35 40 45 50 55 60 65 70 75
(220)
(200)
Inte
nsity
°2q
(111)
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 2914.11.2017 www.helsinki.fi/yliopisto
HTXRD examples– crystallization
• ALD grown tantalum oxide is usually amorphous as deposited
• In this case deposited at 325 °C
• heated and measured under nitrogen, crystallizes to orthorhombic
Ta2O5 above 675 °C
from Blanquart, Longo, Niinistö, Heikkilä, Kukli, Ritala, Leskelä, Semicond.Sci.Tehcnol., 27 (2012) 074003(doi: 10.1088/0268-1242/27/7/074003)
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3014.11.2017
www.helsinki.fi/yliopisto
HTXRD examples– crystallization + phase change
from Kärkkänen, Shkabko, Heikkilä, Vehkamäki, Niinistö, Aslam, Meuffels, Ritala, Leskelä, Waser, Hoffmaan-Eifert,Phys.Status Solidi A, 212 (2015), 751-766 (doi: 10.1002/ p s sa .201431489)
• As deposited ZrO2 is somewhat oriented but not very crystalline as
deposited
• The cubic and tetragonal phase can be distinguished around 60 °2q
upon heating and cooling
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3114.11.2017 www.helsinki.fi/yliopisto
HTXRD examples– oxidation
• ALD grown Rh film
• first weak signs of Rh2O3 phase at 475 °C, Rh fully oxidized >700 °C
from Heikkilä, Hämäläinen, Aaltonen, Ritala and Leskelä, Z.Kristallogr.Suppl.,
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3214.11.2017
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HTXRD examples– reduction
• ALD grown IrO2 thin film heated in nitrogen
• Begins to reduce to Ir above 650 °C, fully reduced >750 °C
from Heikkilä, Hämäläinen, Puukilainen, Ritala and Leskelä, ”High temperature XRD study of atomic layer deposited IrO2”,to be submitted
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3314.11.2017 www.helsinki.fi/yliopisto
HTXRD examples– reduction
• By doing a Rietveld refinement on the data, the cell parameters of
the IrO2 and Ir phase can be represented as a function of T
• Possibility to evaluate
thermal expansion
from Heikkilä, Hämäläinen, Puukilainen, Ritala and Leskelä, ”High temperature XRD study of atomic layer deposited IrO2”,manuscript ready
0 200 400 600 800 100063
64
65
66
67
68
69
0 200 400 600 800 1000
3.10
3.12
3.14
3.16
3.18
0 200 400 600 800 10004.40
4.42
4.44
4.46
4.48
4.50
4.52
4.54
3.78
3.80
3.82
3.84
3.86
3.88
55
56
57
58
59
60
61
T (°C)
iridiumV (Å3)a (Å)
iridium oxidea (Å) c (Å) V (Å3)
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3414.11.2017
www.helsinki.fi/yliopisto
HTXRD examples– reduction
• Heating the same film in vacuum lowers the reduction temperature
over 400 °C
• In this case the reduction is complete at 250 °C
• Crystallinity remains poor up to 500 °C
from Heikkilä, Hämäläinen, Puukilainen, Ritala and Leskelä, ”High temperature XRD study of atomic layer deposited IrO2”,manuscript readyTA+PXRD course - High temperature XRD
November 2017, Mikko Heikkilä 3514.11.2017 www.helsinki.fi/yliopisto
HTXRD examples– reduction
• Heating in actual reducing atmosphere (forming gas (10 % H2 in N2)
lowers the reduction temperature a bit more
• Reduction is now complete at 200 °C, and the Ir phase appears to
crystallize better at lower temperatures
from Heikkilä, Hämäläinen, Puukilainen, Ritala and Leskelä, ”High temperature XRD study of atomic layer deposited IrO2”,manuscript readyTA+PXRD course - High temperature XRD
November 2017, Mikko Heikkilä 3614.11.2017
www.helsinki.fi/yliopisto
HTXRD examples– isothermal reduction
• ALD grown Cu2O in forming gas
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3714.11.2017 www.helsinki.fi/yliopisto
HTXRD examples– phase change
• What happens in the figure below? At least three phase changes
• 175 °C, 275 °C and 925 °C
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3814.11.2017
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HTXRD examples– phase change
• Similar phase transitions in TG
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 3914.11.2017
Step -3,0815 % -0,2881 mgResidue 40,3043 % 3,7679 mgLeft Limit 628,30 °CRight Limit 994,16 °CInflect. Pt. 917,57 °CMidpoint 909,26 °C
Step -37,1419 % -3,4723 mgResidue 43,3869 % 4,0561 mgLeft Limit 255,66 °CRight Limit 627,65 °CInflect. Pt. 278,46 °CMidpoint 289,05 °C
Step -19,4574 % -1,8190 mgResidue 80,5288 % 7,5284 mgLeft Limit 34,11 °CRight Limit 255,66 °CInflect. Pt. 192,40 °CMidpoint 185,83 °C
!rodicrodic, 9,3486 mg
%50
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950
%°C^-12
°C50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950
Lab: Timo Hatanpää SystemeRTAMETTLER TOLEDO S
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Quick and dirty intro to XRR
In XRR• the one dimensional scattering potential (SP) perpendicular to the
sample surface is determined (B-B measurement in very smallangles)
• When the material is layered and it’s chemical composition isknown, the SP can be related to the chemical profile or atomicstructure of the layer(s)• ~electron density
• thickness, mass density and roughness of a single or multiplelayers deposited on some substrate material can be determined
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4014.11.2017
www.helsinki.fi/yliopisto
Quick and dirty intro to XRR
Both XRR and XRD are coherent and elastic scattering techniques,but because of the different momentum transfer, the physical reasonfor the interference of reflected waves is different
• in XRR the interference is due to change in the scatteringpotential (or chemical density) wheras in diffraction this is due tothe long range periodical order
• because of this difference, XRR isn’t restricted to crystallinematter
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4114.11.2017 www.helsinki.fi/yliopisto
Quick and dirty intro to XRR– the effect of different parameters
general trends for a single layer• critical angle shifts to higher angles when density increases (left)
• the fringe amplitude increases as well
• fringe separation decreases as the thickness increases (middle)
• some effect on the graph shape around critical angle
• larger roughness decreases the fringe amplitude as the angleincreases (right)
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4214.11.2017
www.helsinki.fi/yliopisto
How about HTXRR?
Very sensitive to changes in the surface and interfaces might make itpossible to observe the
• surface roughness increase upon crystallization of amorphouslayers
• interface diffusion and possible reaction of amorphous multilayers• interdiffusion of amorphous/crystalline layers before crystallization
of the reaction product
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4314.11.2017 www.helsinki.fi/yliopisto
Some HTXRR examples
• indeed it seems that the surface morphology changes at slightly
lower temperatures than the actual oxidation temperature observed
with HTXRD
4429.9.2010
Tox(Ir) > 500 °C
Tox(Rh) > 475 °C Tox(Ru) > 250 °C
44
from Heikkilä, Hämäläinen, Aaltonen, Ritala and Leskelä, Z.Kristallogr.Suppl.,
14.11.2017TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä
www.helsinki.fi/yliopisto
Some HTXRR examples
• For Ho2O3/TiO2 multilayer, the diffusion
between the layers is observed at much
lower temperature than the actual
crystallization
from Kukli, Lu, Link, Kemell, Puukilainen, Heikkilä, Hoxha, Tamm, Hultman, Stern, Ritala, Leskelä, Thin Solid Films, 565(2014) 165-171 (doi: 10.1016/j.tsf.2014 .06.039)
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4514.11.2017 www.helsinki.fi/yliopisto
End of HTXRD
• During the exercise we’ll
• Setup the oven system including gas delivery
• Make a test measurement ín order
• Determine suitable measurement parameters
• identify the substance and determine the angular range based on that
• Start a measurement and analyze the results later
• More examples during the exercises
• Any questions now are appreciated
TA+PXRD course - High temperature XRDNovember 2017, Mikko Heikkilä 4614.11.2017