Preparation of porous ceramic materials based on CaZrO3

Abstract

The present study was devoted to an investigation of the synthesis conditions and the influence of Sn ions on the production of a CaZrO3 porous structure. Porous ceramics based on CaZrO3 with a SnO addition were prepared by means of pressureless sintering. The study presents the influence of the type of the starting materials and the firing procedures on the microstructures of the CaZrO3 materials. Two different firing procedures were applied. The samples were obtained from pure chemical reagents CaCO3 or CaO and ZrO2. SnO was added in the mass fraction of 2 %. The prepared materials were investigated in terms of phase composition with the XRD. The microstructure was analyzed using the SEM/EDS and mercury porosimetry methods. It was found that using CaCO3 in a one-step firing process at 1650°C with a soaking time of 10 h allowed us to obtain porous zirconate ceramics with a porosity of about 44 %. The second synthesis, where CaO was used, allowed us to obtain a porosity of about 36 %. During the firing solid solutions containing Sn ions in CaZrO3 and ZrO2 were formed. No other compounds containing Sn ions were identified. It was found that these ions played a significant role in the formation of a stable porous microstructure. The final materials mainly consisted of CaZrO3 and a small amount of ZrO2. The obtained porous CaZrO3 materials with an excellent oxidation and alkali resistance in a wide temperature range could be potential candidates for the use as membranes and filters. Keywords: calcium zirconate, porous ceramics, solid solution Ta {tudija je namenjena preiskavi razmer pri sintezi in vplivu ionov Sn na izdelavo porozne strukture CaZrO3. Porozna keramika na osnovi CaZrO3 z dodatkom SnO je bila pripravljena s sintranjem brez tlaka. [tudija predstavlja vpliv vrste izhodnega materiala in procesa`ganja na mikrostrukturo materiala CaZrO3. Uporabljena sta bila dva na~ina`ganja. Vzorci so bili izdelani iz~istih kemijskih sestavin CaCO3 ali CaO in ZrO2. Masni dele`dodanega SnO je bil w = 2 %. Fazna sestava pripravljenega materiala je bila analizirana z rentgensko difrakcijo. Mikrostruktura je bila analizirana s SEM/EDS in s porozimetrijo z`ivim srebrom. Ugotovljeno je, da uporaba CaCO3 v enostopenjskem postopku`arjenja 10 h na 1650°C omogo~a pridobitev porozne cirkonske keramike s poroznostjo okrog 44 %. Druga sinteza, kjer je bil uporabljen CaO, omogo~a doseganje poroznosti okrog 36 %. Med`ganjem je nastala trdna raztopina, ki je vsebovala ione Sn v CaZrO3 in v ZrO2. Ni bila ugotovljena nobena druga sestavina, ki bi vsebovala ione Sn. Navedeno je, da ti ioni igrajo pomembno vlogo pri nastanku stabilne porozne mikrostrukture. Kon~ni materiali so vsebovali prete`no CaZrO3 in majhno koli~ino ZrO2. Dobljen porozni kerami~ni CaZrO3-material z odli~no odpornostjo proti oksidaciji in alkalijam v {irokem temperaturnem intervalu je lahko potencialni kandidat za uporabo v obliki membrane in filtrov. Klju~ne besede: kalcijev cirkonat, porozne keramike, trdna raztopina