Zinc Aluminate (ZnAl2O4) by XPSBrian R. Strohmeier

Citation: Surface Science Spectra 3, 128 (1994); doi: 10.1116/1.1247773 View online: http://dx.doi.org/10.1116/1.1247773 View Table of Contents: http://scitation.aip.org/content/avs/journal/sss/3/2?ver=pdfcov Published by the AVS: Science & Technology of Materials, Interfaces, and Processing Articles you may be interested in Enhanced green emission from UV down-converting Ce3+–Tb3+ co-activated ZnAl2O4 phosphor J. Vac. Sci. Technol. B 30, 031401 (2012); 10.1116/1.3696720 Surface Segregation Study of Transparent ZnGa2O4 Films by XPS Surf. Sci. Spectra 8, 303 (2001); 10.1116/11.20020501 Magnesium Aluminate (MgAl2O4) by XPS Surf. Sci. Spectra 3, 121 (1994); 10.1116/1.1247772 CrystalField Spectra of d 3,7 Ions. V. Tetrahedral Co2+ in ZnAl2O4 Spinel J. Chem. Phys. 51, 2904 (1969); 10.1063/1.1672431 Zeeman Effect of Cr3+ in ZnAl2O4 J. Chem. Phys. 51, 1966 (1969); 10.1063/1.1672286

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Zinc Aluminate (ZnAl 2O4) by XPS

Brian R. StrohmeierAlcoa Technical Center, 100 Technical Drive, Alcoa Center, PA 15069-0001

Zinc aluminate~ZnAl4O4, also known as zinc aluminum oxide! is a material that has applicationsas a catalyst and catalyst support. This paper presents the XPS spectra of the major Zn, Al, and Ophotoelectron lines, and the major x-ray induced ZnLMM Auger lines for ZnAl2O4. © 1995American Vacuum Society.

Keywords: catalyst; spinel; XPS; zinc aluminate; zinc aluminum oxide

PACS: 82.80.Pv, 82.65.Jv

Accession # 00175

Technique: XPS

Host Material: zinc aluminum oxide(zinc aluminate)

Instrument: Kratos Analytical XSAM800

Major Elements in Spectrum: O, Al,Zn

Minor Elements in Spectrum: C

Printed Spectra: 7

Spectra in Electronic Record: 8

Spectral Category: technical

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SPECIMEN DESCRIPTION

Host Material: zinc aluminum oxide~zinc aluminate!

CAS Registry #: 12068-53-0

Host Material Characteristics: homogeneous; polycrystalline;dielectric; inorganic compound; powder

Chemical Name: zinc aluminum oxide

Source: see entry for History & Significance

Host Composition: ZnAl2O4

Form: powder, freshly ground

Structure: normal spinel, cubic close packed

History & Significance: The ZnAl2O4 material used in this studywas prepared by the author in 1981 at the University of Pittburgh, Pittsburgh, PA~see Ref. 1!. ~The powder had beenstored in a glass bottle since that time.! The ZnAl2O4 wasoriginally prepared by mixing stoichiometric amounts of zinoxide ~ZnO, 99.99%, Alfa Products! and g-aluminum oxide~Al2O4, Harshaw Chemical Co., Alumina #AL-1401P, BETsurface area 195 mg2/g! with a small amount of deionizedwater. The resulting mixture was mulled into a paste, dried f8 h at 110 °C, finely ground with a mortar and pestle, and thcalcined for 72 h at 900 °C. The calcined powder was repeedly washed with a 1 M ammonium carbonate@~NH4!2CO3#solution to remove any unreacted ZnO, rinsed with deionizwater, filtered, and dried for 12 h at 110 °C. An x-ray diffraction pattern was obtained from the ZnAl2O4 just prior to theXPS analyses. The diffraction pattern exactly matched tASTM powder diffraction file for ZnAl2O4. No ZnO or Al2O3phases were detected by XRD, which indicates that the samhad not decomposed significantly since preparation. The poder was freshly ground with a mortar and pestle just prior to tXPS analyses.

As Received Condition: powder in glass container

Analyzed Region: same as host material

Ex Situ Preparation/Mounting: The powder was freshly groundwith a mortar and pestle, and spread with a stainless stspatula onto double-sided tape. Past experience with tmounting method has shown that contributions to XPS spetrum from the tape are insignificant.

In Situ Preparation: none

Preanalysis Beam Exposure: none. Data collection commencedas soon as the x rays were turned on.

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Charge Control: none

Temp. During Analysis: 295 K

Pressure During Analysis: ,1.33310–6 Pa

SPECTROMETER DESCRIPTION

Manufacturer and Model: Kratos Analytical XSAM 800

Analyzer Type: spherical sector

Detector: single channel electron multiplier~Galileo model 4816!

INSTRUMENT PARAMETERS COMMON TO ALL SPECTRA

j SpectrometerAnalyzer Mode: constant retard ratio

Throughput ( T5EN): N50.7

Excitation Source: Mg Ka

Excitation Source Window: 0.8mm Al window

Source Strength: 225 W

Source Beam Size: 10 mm3 10 mm

Analyzer Width 2000mm 3 8000mm

Signal Mode: pulse single channel

j GeometryIncident Angle: 70°

Source to Analyzer Angle: 70°

Emission Angle: 0°

Specimen Azimuthal Angle: 0°

Acceptance Angle from Analyzer Axis: 0°

Analyzer Angular Acceptance Width: 2° 3 2°

DATAANALYSIS METHOD

Energy Scale Correction: No energy scale correction was ap-plied to the survey spectrum. The narrow scan spectra werereferenced to the adventitious hydrocarbon C 1s peak at 285.0eV. Because the ZnAl2O4 sample was insulating, the calibrationmeasurements with the Au, Cu, and Ag foils were used only toverify the linearity of the energy scale and to demonstrate thetypical instrument resolution~FWHM!. The binding energymeasurements for the Au, Cu, and Ag specimens were within0.1–0.2 eV or less of the binding energy values that have been

© 1995 American Vacuum Society3(2)/128/7/$1.00/termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32

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recommended in the literature for instrument calibration~seeRef. 2!.

Peak Shape and Background Method: Peak areas~eV-cts/s!were determined using standard Kratos software~DS800, Ver-sion V! and a linear background subtraction~without smooth-ing!. The FWHM and peak amplitude values listed in the Spetral Features Table for the Zn 3p3/2 peak are for the entire Zn3p spin-split doublet. The FWHM value listed in the AnalyzeCalibration Table for the Cu 3p3/2 peak was obtained by curvefitting the broad spin-split Cu 3p doublet with two componentshaving mixed Gaussian/Lorentzian~80%/20%! line shapes anda Shirley-type background.

Quantitation Method: Quantitative calculations~at. %! were per-formed using standard Kratos software~DS800, Version V! andthe appropriate peak areas measured from the narrow sspectra. Relative elemental sensitivity factors for the KratXSAM 800 instrument were calculated from the instrumetransmission function~constant retard ratio mode! and theScofield photoionization cross sections as described in RefThe peak area results indicated that carbon contamination bup on the sample during the XPS analyses, because the Cspeak had a greater peak area than the O 1s peak in the narrowscan spectra, which was not the case in the survey spectrThis carbon overlayer would tend to attenuate the O 1s signalto a greater extent than the Al 2p and Zn 3s signals, because ofthe differences in kinetic energy between these peaks; howe

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this attenuation effect did not affect the quantitative resultssignificantly. The assumed uniform carbon overlayer was ex-cluded from the quantitative analysis to simplify comparison ofthe quantitative results to the theoretical Zn, Al, and O concen-trations. The calculated at. % concentrations for the ZnAl2O4sample~i.e., Zn—15.1%, Al—30.6%, and O—54.3%! were ingood agreement~6 1–3%! with the expected theoretical valuesof Zn—14.3%, Al—28.6%, and O—57.1%.

ACKNOWLEDGMENTS

The author thanks Dr. David Surman, Kratos Analytical, for sup-plying many of the standard instrument parameter values for theKratos XSAM 800 XPS instrument. The author also acknowledgesDr. A. C. Miller, Lehigh University, for calculating the relativeelemental sensitivity factors used in this study.

REFERENCES

1. B. R. Strohmeier and D. M. Hercules, J. Catal.86, 266 ~1984!.2. M. P. Seah, Surf. Interface Anal.14, 488 ~1989!.3. W. Hanke, H. Ebel, M. F. Ebel, A. Joblonski, and K. Hirokawa,

J. Electron Spectrosc. Relat. Phenom.40, 241 ~1986!.4. J. F. Moulder, W. F. Stickle, P. E. Sobol, and K. D. Bomben,

Handbook of X-ray Photoelectron Spectroscopy~Perkin-ElmerCorporation, Eden Prairie, MN, 1992!, p. 18.

SPECTRAL FEATURES TABLE

SpectrumID #

Element/Transition

PeakEnergy(eV)

Peak WidthFWHM(eV)

Peak Area(eV-cts/s)

SensitivityFactor

Concen-tration(at. %)

PeakAssignment

00175-02 Al 2p 74.2 2.05 649 0.555 30.6 ZnAl2O4

00175-02 Zn 3p3/2 89.2 5.02 1009 2.639 ••• ZnAl2O4

00175-03 Al 2s 119.0 2.31 650 0.683 ••• ZnAl2O4

00175-03 Zn 3s 140.0 3.36 485 0.842 15.1 ZnAl2O4

00175-04 Zn 2p3/2 1021.9 1.76 110 1.284 ••• ZnAl2O4

00175-04 Zn 2p1/2 1044.9 2.07 68 0.609 ••• ZnAl2O4

00175-05 Zn 3d 10.6 2.08 461 0.985 ••• ZnAl2O4

00175-05 O 2s 23.0 3.27 207 0.162 ••• ZnAl2O4

00175-06 ZnL3M4,5M4,5 265.9 4.39 2492 ••• ••• ZnAl2O4

00175-06 ZnL2M4,5M4,5 242.9 3.52 970 ••• ••• ZnAl2O4

00175-07 O 1s 531.4 2.25 2132 1.052 54.3 ZnAl2O4

00175-08 C 1s 285 1.97 2624 0.697 ••• hydrocarbon

Footnote to Spectrum 00175-04: The signal intensity of the Zn 2p spectrum is relatively weak compared to the other Zn photoelectronpeaks (i.e., Zn 3s, Zn 3p, Zn 3d, and Zn LMM) because the instrument was operated in the constant retard ratio mode. In this mode, the sensitivityof the electron energy analyzer is proportional to the kinetic energy of the photoelectrons; therefore, the sensitivity at low kinetic energies (highbinding energies) is reduced compared to that at high kinetic energies (low binding energies). The peak at approximately 1014 eV is a C 1s x-rayghost line caused by stray O Ka x rays, which presumably arise from surface oxides present on the Mg anode. O Ka x-ray ghost lines appear at728.7 eV above the main Mg Ka x-ray induced peaks because of the difference in kinetic energy between O Ka and Mg Ka x rays, i.e., 524.9 and1253.6 eV, respectively (see Ref. 4); therefore, the O Ka excited C 1s line appears at 285.0 1 728.7 eV 5 1013.7 eV. No O Ka excited x-ray ghostlines were readily evident in the survey spectrum. The C 1s x-ray ghost line was probably observable in the narrow scan Zn 2p spectrum becausecarbon apparently built up on the ZnAl2O4 sample during the analyses. As the amount of surface carbon built up on the sample, the intensity ofthe O Ka x-ray induced C 1s ghost line increased relative to that observed in the survey spectrum. It should also be noted that the Mg Ka x-raysatellites from the Zn 2p3/2 peak fall under the ghost line at about 1014 eV.

Zinc Aluminate (ZnAl2O4) by XPS 129termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32

ANALYZER CALIBRATION TABLE

SpectrumID #

Element/Transition

PeakEnergy(eV)

Peak WidthFWHM(eV)

Peak Area(eV-cts/s)

SensitivityFactor

Concen-tration(at. %)

PeakAssignment

•••

a Au 4f 7/2 84.0 1.12 ••• ••• ••• •••

•••

b Cu 3p3/2 74.9 2.5 ••• ••• ••• •••

•••

b Cu L3M4,5M4,5 334.9 ••• ••• ••• ••• •••

•••

b Cu 2p3/2 932.7 1.18 ••• ••• ••• •••

•••

c Ag 3d5/2 368.0 0.99 ••• ••• ••• •••

•••

c Ag M4NN 895.7 ••• ••• ••• ••• •••

a Sputtered Au foil.b Sputtered Cu foil.c Sputtered Ag foil.

130 Surface Science Spectra, Vol. 3, No. 2 Zinc Aluminate (ZnAl2O4) by XPS Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32

j Accession #: 00175-01

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: survey

Instrument: Kratos AnalyticalXSAM 800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 24

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 5500 s

Number of Scans: 5

Surface

Science

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o.2Zinc

Alum

inate(ZnA

l2 O4 )by

XPS

131

4.3.164.93 On: Mon, 21 Jul 2014 15:49:32

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j Accession #: 00175-02

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: Zn 3p; Al 2p

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 12500 s

Number of Scans: 50

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

j Accession #: 00175-03

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: Zn 3s; Al 2s

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 12500 s

Number of Scans: 50

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

132 Surface Science Spectra, Vol. 3, No. 2 Zinc Aluminate (ZnAl2O4) by XPS Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32

j Accession #: 00175-04

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: Zn 2p

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 25000 s

Number of Scans: 100

Comment: See footnote below theSpectral Features Table.

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

j Accession #: 00175-05

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: O 2s; Zn 3d

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 12500 s

Number of Scans: 50

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

Surface Science Spectra, Vol. 3, No. 2 Zinc Aluminate (ZnAl2O4) by XPS 133 Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32

j Accession #: 00175-06

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: Zn LMM

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 7500 s

Number of Scans: 30

Comment: The broad peak at about276 eV is caused by the Mg Ka

x-ray satellites from the C 1s peak.

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

j Accession #: 00175-07

j Host Material: zinc aluminumoxide (zinc aluminate)

j Technique: XPS

j Spectral Region: O 1s

Instrument: Kratos Analytical XSAM800

Excitation Source: Mg Ka

Source Energy: 1254 eV

Source Strength: 225 W

Source Size: 10 mm 3 10 mm

Incident Angle: 70°

Analyzer Type: spherical sector

Analyzer Retard Ratio: 53

Analyzer Resolution: 0.2%

Emission Angle: 0°

Data Acquisition Time: 3000 s

Number of Scans: 20

Editor’s Comment: Data as plottedinclude a 1.75 eV charge shiftcorrection.

134 Surface Science Spectra, Vol. 3, No. 2 Zinc Aluminate (ZnAl2O4) by XPS Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 24.3.164.93 On: Mon, 21 Jul 2014 15:49:32