The effect of natural dolomite admixtures on calcium zirconate–periclase materials microstructure evolution

• Published in: Ceramics international Vol. 36; no. 2; pp. 535 - 547
• Main Authors: Szczerba, Jacek, Pędzich, Zbigniew
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2010
• Subjects: Calcium zirconate; Dolomite; Periclase; Refractory materials; Synthesis; Zirconia; Zirconia; Refractory materials; Synthesis; Periclase; Dolomite; Calcium zirconate
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2009.09.025

The reaction sintering mechanism of dolomite–zirconia mixtures was investigated using fine grounded dolomite raw material and zirconium powder. The used dolomite raw materials differed by the content of impurities (SiO 2, Al 2O 3 and Fe 2O 3 oxides). The microstructure evolution of MgO–CaZrO 3 and CaZrO 3 sintered materials was presented as a temperature function. One- and two-step firing processes of calcium raw materials powder mixed with chemically pure zirconium oxide were applied. The kinetics of reaction of CaZrO 3 synthesis was estimated by determining the “free” calcium oxide by chemical and XRD analysis. The densification process was evaluated by firing shrinkage, apparent density, pore diameter and pore size distribution measurements. The microstructure of sintered materials was observed by SEM. It was observed that CaZrO 3 synthesis was definitely finished at temperature of 1500 °C in the both applied ways of the synthesis (one- or two-step process). The only phase present in the model material synthesized from chemically pure reagents (CaCO 3 and ZrO 2) after firing at temperature of 1500 °C was calcium zirconate. In the materials synthesized from natural dolomites and ZrO 2 two main phases were present—calcium zirconate and periclase. During firing of CaZrO 3–MgO materials at lower temperatures the presence of transient phases was detected (mainly ferrites and calcium aluminates, 4CaO·Al 2O 3·Fe 2O 3 or 2CaO·Fe 2O 3). These phases disappeared at higher temperatures. This is probably related to the dissolution of impurities in the main phases of CaZrO 3–MgO. The material obtained from the mixture of zirconium oxide and natural dolomite with the high impurities content has the highest densification level (∼95% theoretical density of CaZrO 3–MgO) at 1500 and 1600 °C.