The aim of the article is to find the optimal fluxing agent for porcelain body regarding to the possibility of the lowest firing temperature. Sintering behaviour of dry pressed test samples made from the mixture of kaolin and three different types of industrially milled feldspar rocks, bone ash and quartz sand with similar granulometry as dependence of water absorption on the firing temperature was investigated. The most intensive fluxing agent for the sintering is bone ash—the mixture containing bone ash (20wt.%) showed sintering temperature 1200 °C. That is about 50 °C lower compared with the most intensive feldspar based fluxing agent—potassium feldspar rock containing 75% of pure microcline

This article examines the process for the synthesis of forsterite–spinel (2MgO·SiO₂/MgO·Al₂O₃) refractory ceramics from fly ash and alumina as sources of aluminum oxide. Raw materials were milled, mixed in different ratios and sintered at 1500 °C for 2 h. Sintered samples were characterized by XRD, thermal analyses and SEM. Porosity, water absorption, bulk density, refractoriness, refractoriness under load and thermal shock resistance were also investigated. The impact of fly ash as a raw material was investigated in accordance with the resulting properties and microstructure of samples with fly ash and alumina as the raw materials. Due to the positive effect of flux oxides (iron oxides and alkalis) on sintering, the mullite contained in fly ash completely decomposed into silica and alumina, which, together with magnesium oxide, formed spinel. This led to improved microstructural and mechanical properties and thermal shock resistance. In particular, mixtures with 10 wt.% and 20 wt.% of fly ash had the most promising results compared to alumina mixtures. Both modulus of rupture and thermal shock resistance were improved, while the impact on refractory properties was minimal. The novelty of this research lies in the recycling of fly ash, a by-product from coal-burning power plants, into a raw material for the production of forsterite–spinel refractory ceramics.

The possibility of natural zeolite utilization as a fluxing agent for sintered ceramic bodies will be determined compared with traditional ceramic flux – feldspar and quartz sand as a grog without fluxing effect. Sintering behaviour as dependence of water absorption of dry pressed test samples made from different fluxes (zeolite, sodium-potassium feldspar) and binder (kaolin) on the firing temperature (1150 – 1300°C) were analysed. Zeolite is very intensive fluxing agent compared with sodium-potassium feldspar. Zeolite with kaolin creates body (after firing) with lower coefficient of linear thermal expansion. Thanks to higher content of ferric oxides is not suitable for whiteware, because the colour of the sintered body is dark (brown)