Sains Malaysiana 47(3)(2018): 581–587
              
            
                http://dx.doi.org/10.17576/jsm-2018-4703-19 
                    
            
               
            
            Sol-gel Synthesis and Optical Properties
              of Malayaite Ceramic Colour Pigments
              
            
            (Sintesis Sol-gel dan Sifat Optik Pigmen Warna
              Seramik Malayait)
              
            
            
               
            
            N. YONGVANICH*, N. WANGWANICH
              & N. PHOMWANA
              
            
            
               
            
            Department of Materials
              Science and Engineering, Silpakorn University, Thailand
              
            
            
               
            
            Received: 30 August
              2016/Accepted: 13 October 2017
              
            
            
               
            
            ABSTRACT
              
            
            Ceramic colour pigments based on the
              malayaite structure was synthesized by sol-gel with an aim to obtain
              homogeneous powder systems. The formulation was Ca(Sn1-xCrx)SiO5 where
              x = 0, 0.02 and 0.05. Thermogravimetric analysis and infrared spectroscopy
              suggested suitable calcination temperatures to be > 1000°C. Formation of
              malayaite phase was found to be very difficult; high calcination temperatures
              up to 1400°C was required which was typical for this particular phase.
              Nevertheless, small amounts of impurities were still present and were found to be
              both wollastonite (CaSiO3) and cassiterite (SnO2).
              The oxidation state of chromium was found to be mainly 4+. The obtained pigment
              particles were in the range of 1-5 micron with a high degree of agglomeration
              due to sintering. UV-vis spectra demonstrated broad
              absorbance peak in the 550-600 nm range which could be attributed to both Cr(III) and Cr(IV). The colour parameters in the CIELab
              system showed a red tone (more positive a* values whereas b* remained
              relatively constant) when chromium was doped into the malayaite host.
              Preliminary interaction testing with a low-fire glaze displayed an even
              improvement in the a* parameter (getting more red
              tone). Microscopic studies showed a certain degree of chromium diffusion out of
              the pigment powders toward the glaze matrix. These results have demonstrated a
              great potential for this refractory colour pigments to be possibly utilized in
              other kinds of glazes as well.
              
            
            
               
            
            Keywords: Ceramics; colour;
              malayaite; pigment; sol-gel
              
            
            
               
            
            ABSTRAK
              
            
                Pigmen warna 
                  seramik berdasarkan struktur malayait disintesis oleh sol-gel 
                  dengan matlamat untuk mendapatkan sistem serbuk homogen. Rumusannya 
                  ialah Ca(Sn1-xCrx) SiO5 
                  dengan x = 0, 0.02 dan 0.05. Analisis termogravimetri 
                  dan spektroskopi inframerah dicadangkan sesuai untuk pengkalsinan 
                  bagi suhu >1000°C. Pembentukan fasa malayait didapati 
                  sangat sukar; suhu kalsinasi yang tinggi sehingga 1400°C 
                  diperlukan secara tipikal pada fasa ini. Walau 
                  bagaimanapun, sejumlah kecil kekotoran masih ada dan didapati 
                  pada kedua-dua wolastonit (CaSiO3) 
                  dan kasiterit (SnO2). Keadaan 
                  pengoksidaan kromium didapati 4+ terutamanya. Zarah 
                  pigmen yang diperoleh berada dalam lingkungan 1-5 mikron dengan 
                  aglomerasi yang tinggi kerana sinteran. Spektrum sinar 
                  UV menunjukkan 
                  puncak penyerapan luas dalam lingkungan 550-600 nm yang boleh 
                  dikaitkan dengan kedua-dua Cr(III) 
                  dan Cr(IV). Parameter warna dalam sistem 
                  CIELab menunjukkan nada merah (lebih 
                  nilai positif a* sedangkan b* kekal agak berterusan) apabila 
                  kromium terdop ke dalam perumah malayait. Ujian interaksi 
                  awal dengan api kecil memaparkan 
                  peningkatan yang lebih baik dalam parameter a* (mendapatkan 
                  lebih banyak nada merah). Kajian mikroskopik 
                  mendedahkan penyerapan darjah tertentu kromium daripada serbuk 
                  pigmen ke arah matriks glas. Keputusan ini telah menunjukkan 
                  potensi yang besar untuk pigmen warna refraktori ini yang mungkin 
                  digunakan dalam jenis glas lain juga. 
                   
            
               
            
            Kata
              kunci: Malayait; pigmen; sol-gel; seramik; warna
              
            
            
               
            
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            *Corresponding author; email: niti.yongvanich@gmail.com