Majid Montazer zohouri; Remy Chapoulie; Mohammadamin Emami
Abstract
Abstractuse of high-energy synchrotron rays in order to identify and characterize historical and cultural materials as accurately as possible, usually in a non-destructive manner and ...
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Abstractuse of high-energy synchrotron rays in order to identify and characterize historical and cultural materials as accurately as possible, usually in a non-destructive manner and with very high accuracy, has become a suitable method to identify the elemental composition of archaeological materials in very small quantities. Furthermore, cathodoluminescence rays can lead to better identification of the chemical composition and phase changes in the historical samples. Cathodoluminescence rays generated from the crystalline compounds lead to new mineralogical interpretations in order to better understand the manufacturing technology and the origin of historical material. In line with the archaeological investigation and studies conducted during the years 1392-1393, a significant number of celadon ceramics, and engraved and glazed pottery were found at the site of Gour. In this research, seven potsherds were examined using conventional laboratory methods and high-energy X-ray beams produced in synchrotron and microscopic cathodoluminescence. These studies were carried out to identify the chemical properties of these ceramics and how they were manufactured. In line with these studies, it was found that these ceramics were made of kaolinite clay and baked at a temperature of ca. 1200 degrees Celsius in two manufacturing stages, and specific proportions of raw materials Si/Al were used in the chemical composition of their body and glaze. This proportion and the method of firing and the condition of the kiln were proof of the coherence and strength of the celadon, which is identical to the temperature interval of the formation of the crystalline phases between the body and the glaze, so-called reaction phase-interphase area.Keywords: The City of Gour, Celadon Ware, Photon Rays, Synchrotron, Cathodoluminescence. 1. IntroductionThe environmental, economic, industrial, and spatial characteristics of the city have been the subject of several detailed studies (Huff, 1970; Huff, 1973; Huff, 2008). The city exhibits a circular urban plan approximately 2 kilometers in diameter, enclosed by two concentric mudbrick ramparts and a surrounding moat. It is connected to the surrounding plain by two perpendicular streets intersecting at the city’s center and features four main gates. Portions of the circular fortification are still preserved, including large governmental and religious structures situated in the city center.Despite the limited number of archaeological excavations conducted in the area, these investigations have produced valuable findings. The most significant research has been carried out by Dietrich Huff and colleagues (Huff and Gignoux, 1978; Karimian and Montazer-Zohouri, 2014). Ceramic sherds represent the most important category of archaeological finds at the site. Research indicates that the ceramics from Ardashir Khurrah date from the late Arsacid and Sasanian periods through the early, middle, and late Islamic periods, spanning approximately the 7th to the 16th/17th centuries CE (Karimian and Montazer-Zohouri, 2014).Studies focusing on the cephalina (citadel) of Ardashir Khurrah have further clarified the chronological range of pottery production in the city. These analyses suggest that ceramic material from the site spans from the late Parthian and Sasanian periods through to the early Islamic centuries and into the middle and late Islamic periods (approximately the 1st through 11th centuries AH / 7th through 17th centuries CE) (Karimian and Montazer-Zohouri, 2014). As such, the ceramic assemblage from Ardashir Khurrah constitutes a critical source for understanding the cultural and historical development of this important ancient city.One of the key types is the celadon wares imported from China. Iran and China had cultural and commercial relations from the pre-Islam period; many archaeological finds indicate this interaction. The China-Iran relationship lasted into the Islamic period; celadon wares are one of the most important sources of evidence on the two commercial cooperation between the two countries. Celadon had been known as a commercial Chinese product in the Islamic lands (Emami et al., 2019). This ware type has a frit body covered with revitalized glaze in the green to brown color range. Celadon ware is a common type in a large number of Islamic sites, distributed across the Iranian Plateau via the main and secondary trade roads from the 7th and 8th to the 16th-17th centuries. The celadon wares found in Ardshirkhoreh are in the green and grey color range and date back to the 13th-14th and the 15th-17th centuries. Similar types have been found at Siraf, Kish, and Rab-e Rashidi (Morgan, 1991, Takahito, 1988). Most celadons are found in the citadel (Arg) and along the eastern street in Ardshirkhowreh. The Chinese celadons have been imported to the area by the southern ports like Siraf and then scattered in the hinterlands city like Ardshirkhowreh. 2. Material and MethodsNew insights on the chemical composition of the stoneware pottery with bluish green glaze so called celadon from Ardeshir-Khore, 4th century AC (Iran) have been achieved by SR-based X-ray diffraction analysis and cathodoluminescence microscopy. Techniques based on synchrotron radiation have been widely applied in archaeology. High-energy synchrotron radiation makes it possible to characterize the composition of the newly formed minute crystalline phases within the matrix of the pottery. At the same time, cathodoluminescence imaging provides new insight into mineralogical criteria that are not visible with the usual optical microscopy approach. However, the tiny crystals which are revealed, can be considered as real markers for the knowledge of important features such as the highest firing temperatures reached at this time. 3. DiscussionCeladon wares are structurally a unique pottery type with numerous chronologically sensitive characteristics. These materials are indications of maritime and land trade from the Far East and China to Iran (Huang et al., 2020, Molera i Marimon et al., 2022). In this regard, the history of the emergence of Celadon in Iran dates back to the Sassanid era and then the peak period of the use of this type of historical pottery in Iran to the Ilkhanid era and the cities of the Persian Gulf: Kerman, Sistan, Jiroft, Kashan, Ray and Qazvin are among the important places for the existence and production of this type of pottery in the Iranian Plateau (Huang et al., 2020, Molera i Marimon et al., 2022, Amirhajloo and Sedighian, 2023, Barnes et al., 2010).The exact characteristics of the geo-chemical fingerprint and phase composition of the primary clay paste is reflected by the re-crystallizations through firing as an important criterion for the “chaîne opératoire” in ceramic technology of the past (Tite et al., 2012). The determinination of newly formed minute crystalline phases by synchrotron XRD is essential, since identification of the reaction products during the firing of primary clay, sometimes cannot be well clarified by routine methods (Emami et al., 2021). Multidisciplinary methods are crucial for determining the primary clay base, as well as the manufacturing processes of these prestigious objects (Cheng et al., 2002). Synchrotron based XRD results enable the characterization of both mineralogical constituents of a pottery and its fabrication by identifying high temperature phases and defining kiln atmosphere conditions. The samples were studied earlier by cathodoluminescence imaging to localize the specific zones of recrystallization and the newly formed crystals. Crystal growth and its statement is revealed by means of the cathodoluminescence color of the minerals and will be interpreted as a generation of high temperature silica and calcium phases such as mullite and anorthite. 4. ConclusionThe composition and structure of the celadon were first observed using the common methods of polarizing microscopy, and then through using high-energy beams of synchrotron and Low-energy rays of cathodoluminescence. Characteristically the results indicate the use of illitic soil with different amounts of carbonate compounds. The cooking temperature of the salads is about 1270 degrees Celsius based on the high temperature phases of the sherds. Moreover, the celadon are made in two stages: first, the body is fired and then the glaze is put on before the body is completely sintered. SR-XRD and CL microscopy have clarified insights into the characterization of high temperature phases in the body and phase-interphase area between the body and the celadon glaze. Anorthite occurred mostly in interphase zones between body and glaze. Over high firing temperature of the celadons (ca. 1200°C), formation of high temperature phases such as mullite and other aluminosilicates, might be notable in association with SiO2/Al2O3 wt% ratios.
