Universidade de Aveiro SarahH.Henry* ,JoaquimM.Vieira ... HENRY... · SEM images of polish...
1
SEM images of polish cross-sections of ceramic shreds in Fig. 2 reveals that the glazes layers of four Universidade de Aveiro SarahH.Henry* 1 ,JoaquimM.Vieira*,MartaC.Ferro*,SusannaGómezMartínez + ,PedroQ.Mantas* •Department, of Materials and Ceramic Engineering, CICECO University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal •+ Campo Archeologico de Mértola, 7750-353Mértola, Portugal, 1 [email protected] PRESENTATION. “Cuerdaseca” is characterized by a black line surrounding the draws, used to separate the different colors of the glaze and to prevent their mixing. The line is made of a mixture of manganese oxide and a fat that burns during firing, leaving the black mark. Studies have already been conducted on the cuerdaseca(Susana Gomez), but many areas remain to be explored. In this study, the generally aim is to contribute to identification of origin and fabrication process of a set of six pieces of Islamic ceramics from the X-XIIIthcenturies from Mértolaarcheological site by the characterization of composition and microstructure of pastes and glazes. EXPERIMENTAL METHODS . The following techniques of characterization of materials were used in this study of the six ceramic shreds: UV-spectroscopy and colorimetric analyses, to measure color indexes of the pastes; powder X-ray diffraction (XRD) to identify the crystalline phases in the pastes; cold-field electron gun Scanning Electron Microscopy with chemical element microanalysis (SEM/EDS) with ZAF correction to determine the morphology and approximate elemental composition, and obtain EDS line scan profiles of glazes, interfaces, paste and other morphological features, such as weathering layers found on polished cross-sections of the shreds; Micro-Raman spectrometry for chemical bond characterization of selected samples. CR/CSP/0023 HBR-0206 HBR-0001 CR/CSP/0022 HBR-0207 HBR-0072 a b c HBR-0072 HBR-0207 CR/CSP/0022 HBR-0001 HBR-0206 CR/CSP/0023 L* 79.92 97.33 50.11 55.49 51.67 55.76 a* -4.96 -4.77 -2.39 5.43 10.25 9.10 b* 27.26 27.01 18.14 22.89 27.28 25.83 MINERALS TRANSFORMATION Metakaolin: Al2Si2O7 Temperature of formation: 550-600°C Mullite: Al6Si2O13 Temperature of formation: 1050°C Gehlenite: Ca2Al2SiO7 Chemical reaction: + Temperature= 800°C 0,7 0,8 0,9 CaO 0.8 0.9 1.0 HBR-0001 SHAS-02 phase-separation CLx+BA MAIN RESULTS . The panel in Fig.1 is composed of 6 samples from between the XIthand XIIIth centuries. Two pieces were found under the Christian cemetery (CR/CSP/0022 , /0023) and four in a septic pit outside the city walls (HBR-0001, /0072, /0206/ 0207). Four samples are partial “cuerdaseca”, of the remaining ones (HBR-0207) is total “cuerdaseca”. To where HBR-0072 belongs is unclear. Values of the CIEL*a*b* color coordinates of the pastes determined on polished cross-sections of the 6 samples are given the table 1, the corresponding RGB color is represented in the headings. The phase composition (XRD) and EDS micro-analysis results are given in Table 2. Firing temperatures can be inferred from clay mineral transformation temperatures in Table 3. Fig.1 Photography images of the six ceramic shreds Table 1. CIE L*a*b* color coordinates of the 6 pastes Table 2. (XRD) phase composition and EDS microanalysis results of the 6 pastes Table 3. Clay mineral transformation as a function of temperature firing (Cultrone 2001) shreds in Fig. 2 reveals that the glazes layers of four samples are well preserved (HBR-0072, /0207, /0208 and CR/CSP/0022). They have homogeneous chemical element composition, table 4. The glazes of samples CR/CSP/0023 and HBR-0001 have complex multiple layer structures and one of these structures shows a trend for rapid weathering and it has high phosphate contents of very constant ratio of the elements Pb/P/Ca; as shown in Fig. 3. The results of EDS line profile analysis of structures inside glaze layers of samples CR/CSP/0023 and HBR-0001 reveal gradients of chemical composition and, after numerical filtration, and proved to be strongly correlated, Fig. 4. Micro-Raman results in Fig.5 indicate that zoned P rich volumes can by a (Pb,Ca) HPA solid solution, or hydroxipyromorphite, precipitated at pH 6-8, by fixing Pb2+ ions of the solution under the effect of dissolved bone HPA material , giving the observed (micro-Raman/EDS) (Pb 2 ,Ca 3 )(PO 4 ) 3 OH compound at (pH ~6) (Crannell 2000), X CICM2 | SILVES |22 a 27 .outubro.2012 DISCUSSION AND CONCLUSIONS. Samples can grouped by their similarities color, mullitecontent/absence , iron concentractionin the pastes, or by quality of the glaze, Sncontents/absence , layer structure or the morphology phosphor containing areas of their glazes. Whichever the criteria, the samples CR/CSP/0023 and HBR-0001 make a special group, because they showed a visible stratigraphiceffect, that look like precipitates of phosphorous matter, which deserves to be further studied. It is generally accepted that the phosphorous matter in archaeological ceramics comes from runoff water, or more general weathering (Clare Déléry, 2009). However, from the results obtained here one may wonder if bone ashes as raw material for low melting point ceramic glazes were already in use. The Acknowledgements: -Support from FAME Master/Erasmus Mundus -Access to the electron microscope infrastructure of RNME Pole of Aveiro, FCT Project: REDE/1509/ RME/2005 - Mertola Archeological Site for providing the archeologicalceramic shreds Calcium oxide Anorthite: CaAl2Si208 Temperature= 900°C CR/CSP/0023 HBR-0206 HBR-0001 CR/CSP/0022 HBR-0207 HBR-0072 a b c 0 0,1 0,2 0,3 0,4 0,5 0,6 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 PbO PO5/2 0.1 0.4 0.7 0.2 0.3 0.5 0.6 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 0 0,1 0,2 0,3 0,4 0,5 0 ,6 0 ,7 0,8 0,9 1 MG PbO CaO SiO2 0.1 0.4 0.7 0.2 0.3 0.8 0.5 0.6 0.9 1.0 HBR-0001 SHAS-02 phase-separation CLx+BA Fig.3. Plotting of the EDS results of sample HBR-0001 in ternary phase diagrams. a) The PbO-PO 5/2 - CaO system. b) The PbO-CaO-SiO 2 system. Projections: MG –glass miscibility gap; GF –phosphate glass forming range; Clx+BA –Pb calxand bone ash in equal weight amounts 0 0.2 0.4 0.6 0.8 0.2 0.4 0.6 0.8 Pb-P-SiOx ternary phase diagram PbO PO5/2 SiO2 Gd〈〉 pltsf〈〉 plqf 〈〉 plc〈〉 Gd〈〉 pltsf〈〉 , plqf 〈〉 , plc〈〉 , wb 1.5 = 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 Intensity (a. u.) Intensity (a. u.) Wavenumber / cmHAP a a4 Quartz Quartz_edge a6_interface HAP Glaze/bodyinterface Quartz,edge Quartz Zoning areas (a4) spherical inclusion Table 4. EDS microanalysis average results of glaze and glaze/ paste interface zone of the six ceramic shreds Fig.2 SEM images of polish cross-sections of the six ceramic shreds Fig.4 SEM (BSE image) of the sample HBR-0001, details on a phosphorous grain and its line scan; in pink Si, in red P, in green Pb, in brown Ca, in blue C, in purple Fe, in turquoise Cu and in grey Sn, and plot of element concentration in ternary phase representation. Fig.5. Micro-Raman spectra of phosphate-rich and quartz inclusions, banded matrix area and glaze/ paste interface of sample HBR-0001, and reference micro- Raman spectra of pure (HAP) (courtesy of Dr. Diogo Mata), λo = 532 nm. presence of calcium phosphate in he body and glaze of ancient ceramics was early explained in Kingery and Freestone works (Kingery1984; Freestone 1998) as linked to the practice of adding bone ash in making white enamels, said to be an Islamic technique of opacification, the process being recognized in Islamic enameled glasses from 13-14th century and in the production of some Iznikceramics (Anatolia, Turkey), (Henderson 1989). From such perspective, the distinction between technical phosphor and phosphate sediments needs to be made. (apologies: cited references in separate page )
Transcript of Universidade de Aveiro SarahH.Henry* ,JoaquimM.Vieira ... HENRY... · SEM images of polish...
SEM images of polish cross-sections of ceramic
shreds in Fig. 2 reveals that the glazes layers of four
Universidade de Aveiro Sarah H. Henry*1, Joaquim M. Vieira*, Marta C. Ferro*, Susanna Gómez Martínez+, Pedro Q. Mantas*•Department, of Materials and Ceramic Engineering, CICECO University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
•+ Campo Archeologico de Mértola, 7750-353Mértola, Portugal,1 [email protected]
PRESENTATION. “Cuerda seca” is characterized by a black line surrounding
the draws, used to separate the different colors of the glaze and to prevent their
mixing. The line is made of a mixture of manganese oxide and a fat that burns
during firing, leaving the black mark.
Studies have already been conducted on the cuerda seca (Susana Gomez), but
many areas remain to be explored. In this study, the generally aim is to
contribute to identification of origin and fabrication process of a set of six pieces
of Islamic ceramics from the X-XIIIth centuries from Mértola archeological site
by the characterization of composition and microstructure of pastes and glazes.
EXPERIMENTAL METHODS. The following techniques of characterization of
materials were used in this study of the six ceramic shreds: UV-spectroscopy and
colorimetric analyses, to measure color indexes of the pastes; powder X-ray
diffraction (XRD) to identify the crystalline phases in the pastes; cold-field
electron gun Scanning Electron Microscopy with chemical element
microanalysis (SEM/EDS) with ZAF correction to determine the morphology and
approximate elemental composition, and obtain EDS line scan profiles of glazes,
interfaces, paste and other morphological features, such as weathering layers
found on polished cross-sections of the shreds; Micro-Raman spectrometry for
chemical bond characterization of selected samples.
CR/CSP/0023 HBR-0206 HBR-0001
CR/CSP/0022 HBR-0207 HBR-0072
a
b c
HBR-0072 HBR-0207 CR/CSP/0022 HBR-0001 HBR-0206 CR/CSP/0023
L* 79.92 97.33 50.11 55.49 51.67 55.76
a* -4.96 -4.77 -2.39 5.43 10.25 9.10
b* 27.26 27.01 18.14 22.89 27.28 25.83
MINERALS TRANSFORMATION
Metakaolin: Al2Si2O7 Temperature of formation: 550-600°C
Mullite: Al6Si2O13 Temperature of formation: 1050°C
Gehlenite: Ca2Al2SiO7 Chemical reaction: + Temperature= 800°C 0,7
0,8
0,9 CaO
0.8
0.9
1.0HBR-0001
SHAS-02
phase-separation
CLx+BA
MAIN RESULTS. The panel in Fig.1 is composed of 6 samples from between the
XIth and XIIIth centuries. Two pieces were found under the Christian cemetery
(CR/CSP/0022 , /0023) and four in a septic pit outside the city walls (HBR-0001,
/0072, /0206/ 0207). Four samples are partial “cuerda seca”, of the remaining
ones (HBR-0207) is total “cuerda seca”. To where HBR-0072 belongs is unclear.
Values of the CIEL*a*b* color coordinates of the pastes determined on polished
cross-sections of the 6 samples are given the table 1, the corresponding RGB
color is represented in the headings. The phase composition (XRD) and EDS
micro-analysis results are given in Table 2. Firing temperatures can be inferred
from clay mineral transformation temperatures in Table 3.
Fig.1 Photography images of the six ceramic shreds
Table 1. CIE L*a*b* color coordinates of the 6 pastes
Table 2. (XRD) phase composition and EDS microanalysis results of
the 6 pastes
Table 3. Clay mineral transformation as a function of temperature
firing (Cultrone 2001)
shreds in Fig. 2 reveals that the glazes layers of four
samples are well preserved (HBR-0072, /0207,
/0208 and CR/CSP/0022). They have homogeneous
chemical element composition, table 4. The glazes of
samples CR/CSP/0023 and HBR-0001 have complex
multiple layer structures and one of these structures
shows a trend for rapid weathering and it has high
phosphate contents of very constant ratio of the
elements Pb/P/Ca; as shown in Fig. 3. The results of
EDS line profile analysis of structures inside glaze
layers of samples CR/CSP/0023 and HBR-0001
reveal gradients of chemical composition and, after
numerical filtration, and proved to be strongly
correlated, Fig. 4.
Micro-Raman results in Fig.5 indicate that zoned P
rich volumes can by a (Pb,Ca) HPA solid solution, or
hydroxipyromorphite, precipitated at pH 6-8, by
fixing Pb2+ ions of the solution under the effect of
dissolved bone HPA material , giving the observed
(micro-Raman/EDS) (Pb2,Ca3)(PO4)3OH compound
at (pH ~6) (Crannell 2000),
X CICM2 | SILVES |22 a 27 .outubro.2012
DISCUSSION AND CONCLUSIONS. Samples can grouped by their similarities
color, mullite content/absence , iron concentraction in the pastes, or by quality
of the glaze, Sn contents/absence , layer structure or the morphology phosphor
containing areas of their glazes. Whichever the criteria, the samples
CR/CSP/0023 and HBR-0001 make a special group, because they showed a
visible stratigraphic effect, that look like precipitates of phosphorous matter,
which deserves to be further studied.
It is generally accepted that the phosphorous matter in archaeological ceramics
comes from runoff water, or more general weathering (Clare Déléry, 2009).
However, from the results obtained here one may wonder if bone ashes as raw
material for low melting point ceramic glazes were already in use. The
Acknowledgements:
- Support from FAME Master/Erasmus Mundus
-Access to the electron microscope infrastructure of
RNME Pole of Aveiro, FCT Project: REDE/1509/
RME/2005
- Mertola Archeological Site for providing the
archeological ceramic shreds
Chemical reaction: + Calcium oxide Anorthite: CaAl2Si208 Temperature= 900°C
CR/CSP/0023 HBR-0206 HBR-0001
CR/CSP/0022 HBR-0207 HBR-0072
a
b
c
0
0,1
0,2
0,3
0,4
0,5
0,6
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
PbO PO5/2
0.1
0.4
0.7
0.2
0.3
0.5
0.6
CLx+BA
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
MG
PbO CaO
SiO2
0.1
0.4
0.7
0.2
0.3
0.8
0.5
0.6
0.9
1.0HBR-0001
SHAS-02
phase-separation
CLx+BA
Fig.3. Plotting of the EDS results of
sample HBR-0001 in ternary
phase diagrams. a) The PbO-PO5/2-
CaO system. b) The PbO-CaO-SiO2
system. Projections: MG – glass
miscibility gap; GF – phosphate
glass forming range; Clx+BA – Pb
calx and bone ash in equal weight
amounts
0 0.2 0.4 0.6 0.8
0.2
0.4
0.6
0.8
Pb-P-SiOx ternary phase diagram
PbO PO5/2
SiO
2
Gd 1⟨ ⟩
pltsf1⟨ ⟩
plqf 1⟨ ⟩
plc 1⟨ ⟩
Gd 0⟨ ⟩ pltsf 0⟨ ⟩, plqf 0⟨ ⟩, plc 0⟨ ⟩,
wb 1.5=
0,4
0,5
0,6
0,7
0,8
0,9
1
1,1
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Inte
nsi
ty (
a. u
.)
Int
en
sit
y (
a.
u.)
Wavenumber / cm- 1
HAP
a
a4
Quartz
Quartz_edge
a6_interface
HAP
Glaze/body interface
Quartz,edge
QuartzZoning areas (a4)
spherical inclusion
Table 4. EDS microanalysis average results of glaze and glaze/
paste interface zone of the six ceramic shreds
Fig.2 SEM images of polish cross-sections of the six ceramic shreds
Fig.4 SEM (BSE image) of the sample HBR-0001, details on a phosphorous
grain and its line scan; in pink Si, in red P, in green Pb, in brown Ca, in blue
C, in purple Fe, in turquoise Cu and in grey Sn, and plot of element
concentration in ternary phase representation.
Fig.5. Micro-Raman spectra of
phosphate-rich and quartz
inclusions, banded matrix area and
glaze/ paste interface of sample
HBR-0001, and reference micro-
Raman spectra of pure (HAP)
(courtesy of Dr. Diogo Mata), λo =
532 nm.
presence of calcium phosphate in he body and glaze of
ancient ceramics was early explained in Kingery and
Freestone works (Kingery 1984; Freestone 1998) as linked to
the practice of adding bone ash in making white enamels,
said to be an Islamic technique of opacification, the process
being recognized in Islamic enameled glasses from 13-14th
century and in the production of some Iznik ceramics
(Anatolia, Turkey), (Henderson 1989). From such
perspective, the distinction between technical phosphor and
phosphate sediments needs to be made.
(apologies: cited references in separate page)
