شناسایی ترکیبات لعاب‌های به‌کار‌رفته در آجرهای لعاب‌دار تخت‌جمشید با تاکید بر لعاب سبز و زرد

لعاب مادۀ جدیدی نیست و سال هاست که بشر با آن آشناست. لعاب ها طیف گسترده ای از ترکیبات آلی و معدنی را دربر می گیرند. این پژوهش درخصوص شناسایی لعاب آجرهای لعاب دار هخامنشی در تخت جمشید است که تاکنون برروی این آجرها مطالعاتی در زمینۀ معرفی انجام پذیرفته، اما مطالعات فنی جامعی درمورد شناسایی ترکیبات لعاب های آن ها صورت نگرفته است. لعاب های مورد استفاده در آجرهای سفالی تخت جمشید به رنگ های سفید، سبز کم رنگ، سبز پر رنگ، قهوه ای تیره، خاکستری و زرد حنایی رنگ آمیزی شده اند، که در این پژوهش لعاب های سبز کم رنگ و سبز پر رنگ و زرد حنایی سربی مورد بررسی قرار گرفته اند. این پژوهش که از نوع تجربیآزمایشگاهی با استناد به مدارک معتبر علمی است، با هدف شناخت عناصر تشکیل دهندۀ لعاب ها در آجرهای لعاب دار هخامنشی در تخت جمشید انجام پذیرفته و پرسش اصلی این است که عمده ترین عوامل رنگ کننده در لعاب های سبز کم رنگ و سبز پر رنگ و زرد حنایی در این آجرسفال ها چیست؟ در این راستا با استفاده از روش های xrd, sem, dta و tga و آنالیز شیمیایی تر بدنه و لعاب ها شناسایی شد که بدنۀ این نوع آجرها یک بدنۀ سیلیسی و به صورت بسیار متخلخل است. با توجه به آزمایشات صورت گرفته، نتایج به دست آمده در این پژوهش نشان می دهند که در ترکیب تمامی لعاب ها آهن و منیزیم وجود دارد که احتمالاً در ترکیب اصلی (لعاب پایه) غیر از اثرات رنگی به صورت ناخالصی وجود داشته اند.

Identification of Glaze Compositions Used in Persepolis Glazed Bricks Emphasizing Green and Yellow Glazes

AbstractGlaze is not a new material and human beings have been familiar with it for many years. Glazes contain a wide range of organic and inorganic compounds. This research is about identifying the glazes of Achaemenid glazed bricks in Persepolis. So far, studies have been conducted on these bricks in the field of introduction, but comprehensive technical studies have not been done on identifying the composition of their glazes. The glazes used in Persepolis clay bricks are painted in white, light green, light green, dark brown, gray and fawn yellow. In this study, light green, light green and yellow fawn glazes were investigated. This research, which is of experimentallaboratory type with reference to valid scientific documents, has been carried out with the aim of identifying the constituent elements of glazes in Achaemenid glazed bricks in Persepolis. What are these bricks? In this regard, using XRD, SEM, DTA and TGA methods and more chemical analysis of the body and glazes, it was identified that the body of this type of brick is a siliceous body and very porous. According to the experiments, the results obtained in this study show that iron and magnesium are present in the composition of all glazes, which may have been present in the main composition (base glaze) in addition to color effects as impurities.Keywords: Takhtejamshid, Glazed Bricks, Chemical Methods, Green Glaze, Yellow Glaze, Lead Glaze.IntroductionPersepolis is undoubtedly one of the most magnificent monuments of the ancient world. Glazed bricks were found by Schmidt in various parts of the building, some of which are in the Museum of Ancient Iran and some in other museums, including the Persepolis Museum. The examples studied in this study are located in the eastern wall of the Women’s Palace during the reign of Xerxes, which is now used as the administrative building of Marvdasht Cultural Heritage. The glazed bricks discussed in this study include the parts of the eastern wall of the palace where the glazing of the bricks of these parts is siliceous. Are examined and the necessity of conducting this research is the repair and protection of these glazed bricks. In the present research, the following questions have been answered: 1 What are the components and main coloring factors in light green, light green and fawn yellow glazes in these glazed bricks? 2 What are the components of the body in these glazed bricks? There are different methods for identifying materials. In this study, because most of the colors have been identified, more attempts have been made to use the methods used to identify and analyze the composition of materials, because this study aims to identify the constituent elements of glazes in Achaemenid glazed bricks. In Persepolis and is of experimentallaboratory type with reference to valid scientific documents and conducting library studies and visiting the historical site of Persepolis, which in this regard were identified using XRD, SEM, DTA, TGA body and glaze methods and the most important The coloring agents of these glazes were identified.Introducing ExamplesThe samples were very small that after sampling were in the form of flakes and to prepare the test in powder form. Tests performed on samples Immersion tests were performed on two small pieces of body: sample volume, bulk density and volume weight. In addition, more chemical analysis was performed on the samples, which in total showed that about 79% of Sio2 (silica) and 16% of Ca2o3 (calcium oxide) in the body. On the body sample, XRD test, DTA test (thermal analysis) and TGA test (weight change) were also performed. Green Dye Oxides A mixture of copper oxide and lead glaze, compared to the chemical composition of the glaze, can produce a variety of green colors. The sample (bold green) was first subjected to XRD test. Also, light green color was tested by XRD and SEM and the results were obtained. In bright green, it shows the presence of two phases of quartz Sio2 and “hydin bergite” Ca (Fe, Mn) Si2o6 In fact, the main phase of both light green and light green is the same, and the percentage of colorants in the composition is probably different. Green The presence or absence of another element can reduce or increase the color of green. Studies show that copper causes blue in alkaline glazes and green in lead glazes. Yellow Glaze Dye Oxides In leadrich acid glazes, the addition of a very small amount of chromium oxide, up to 1% at low temperatures, results in a yellow color. The combination with Cao and Sno2 can also give a pink color. Also, Tio2 titanium oxide makes lead glazes yellow and leadfree glazes white. The yellow glaze was subjected to XRD test and also SEM test was performed on the above sample. The results show that the yellow color consists of two phases, one CdPbo3 and one quartz phase with a low crystallization percentage. The presence of Pb (lead) is a clear reason for the yellow lead of the glaze, which is one of the main reasons for the greater transparency of the yellow glaze than other glazes. Titanium oxide makes lead glazes yellow, and here we have a lead glaze containing titanium oxide. Therefore, titanium oxide can be mentioned as a possible yellowing agent in this glaze.Conclusion The body of the glazed bricks in Persepolis, which has been studied in this study, looks very porous and is milky in color and shiny like flint. The results of the samples are analyzed and the following points can be stated: XRD test on these bricks confirmed that the body was siliceous, and according to the TGA test, it can be said that calcium carbonate was converted to calcium oxide, and weight loss was also the result of this conversion. The green and yellow glazes were lead. The reason for the gloss of these glazes compared to other glazes is that they are lead, and their transparency is still clear. All glazes contained iron and magnesium, which may have been impurities in the main composition of the base glaze, apart from its color effects. XRD test on green glazes shows the presence of two phases Sio2 and Ca (Fe, Mn) Si2o6. The coloring agent in this glaze is Cu, which is almost more noticeable than other elements (except Si and Ca). Therefore, due to the lead content of the glaze, the presence of copper in this lead glaze causes a green color. The presence of Ca in green glazes causes the color of the glaze to become opaque, and it can be said that one of the reasons for being bright or light is the difference in the percentage of Cao. SEM test of yellow glaze detected the presence of Pb elements from Pbo, K from Kcl, Cr from Cr2o3, Ca from Cao Fe from Fe2o3, Al from Al2o3 and Ti from Tio2. The presence of Pb is one of the main reasons why this glaze is more transparent and leadfree than other glazes, and in leadrich acid glazes, adding a very small amount of Cr2o3 up to one percent at low temperatures, turns yellow. Titanium oxide also makes lead glazes yellow, so titanium oxide can be mentioned as a possible yellowing agent in this glaze, and the presence of iron has made this color tend to be fawn.