SrO (Strontium Oxide, Strontia)

Notas

Strontium oxide (SrO) is a basic oxide within the alkaline earth group, characterized by a cubic crystal structure. While raw strontium carbonate decomposes to release SrO, its significant melting point—exceeding 1100°C—necessitates the use of fritted sources to achieve effective fluxing at lower temperatures. Functionally, SrO acts as an essential lead-free and non-toxic alternative to lead or barium, capable of producing brilliant, high-gloss surfaces even at low-fire ranges like cone 01. In stoneware glazes, it promotes a strong interface with the clay body, likely due to the mixed-oxide effect, and contributes to craze resistance. Because of its high refractive index, substituting SrO for calcium oxide often increases glaze gloss. While it can produce vivid color responses with transition metals such as copper and cobalt, its impact on color differs from that of CaO. Although SrO shares a similar thermal expansion profile with CaO, its use as a total replacement for BaO requires careful attention to body-glaze fit, as differences in elasticity may occur. When SrO serves as the dominant flux in the RO group, it can promote crystal matte surfaces during cooling, though incorporating a diverse blend of fluxing oxides will inhibit this crystallization. Furthermore, small additions of SrO are effective for improving the surface quality of viscous, high-fire zirconium-opacified glazes.