Multicomponent solid solutions based on zirconium dioxide

Abstract

Solid solutions of rare-earth and alkaline-earth oxides in ZrO 2 are well known as highly refractory materials which show anionic conduction with a transport number close to unity over a wide range of temperatures and oxygen pressures,The formation conditions and the properties of solid solutions in the following systems have been studied most fully: ZrO2--CaO; ZrO2--MgO; ZrO2--Y203; and ZrO2--SC203. These have been studied particularly well in the region of high concentrations of ZrO 2 [1-4]. The solid solutions of 8-9 mole% of Y203 or Sc203 in ZrO 2 are the most promising materials on the basis of their resistance to destabilization and the absolute values of their conductivity, However, the wider use of such materials is limited because of their cost, particularly in the case of Sc203.We have studied the four-component solid solutions ZrO2--Y203--CaO--MgO with the aim of producing a material which would be resistant to destabilization and would have an electrical conductivity on the same level as the optimum solid solution in the ZrO2--Y203 system (~15% by mass of Y203) but with a lower concentration of yttrium oxide.Oxides of calcium, magnesium, and yttrium in the ratios shown in Table 1 were dissolved in a melt of zirconyl chloride octahydrate ZrOC12" 8H20 at 110-120~ Ammonia and ammonium carbonate were then added to the solution and it was stirred vigorously [5]. The concentration of the ammonia was 100 g NH 3 per liter; the ammonium carbonate was used in amounts 1.5 times greater than that required to bond the calcium and magnesium into the appropriate carbonates [6]. The suspension (temperature 90~ pH = 8.5-9) was

Porous ceramic concrete based on zirconia as a high-temperature heat-insulant

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The Eastern Institute of Refractories has designed a resistance heater from stabilized zirconium dioxide for use in oxidizing atmospheres at temperatures of up to 2500~ [1][2][3], ana has designed furnaces based on it [4][5][6][7].These furnaces are particularly valuable for firing ceramics, growing single crystals, and forming quartz fiber [8][9][10].Experience with these furnaces has shown that to reduce the inertia and increase the working reliability of the heaters it is extremely important to use linings which possess a range of properties which are, in fact, very difficult to combine: application temperature up to 2500~ high resistance to creep, good thermal-shock resistance, and low thermal conductivity and specific heat.Materials based on magnesium and aluminum oxides are unsuitable for these purposes, so zirconia was used to make high-temperature insulation; this has a high refractoriness and low thermal conductivity.Previously [Ii], it was shown that stabilized zirconia obtained by the combined precipitation of components from aqueous solutions, together with a high homogeneity and sintering activity, possesses cementing properties, which means it can be used for making refractory concretes.The technology involved the use of the principles for obtaining porous ceramic concretes [12,13], foamed ceramic from Zr02 [14], and the use of foamed polystyrene to obtain spherical pores in the ceramic products [15].The technology for producing porous ceramic concrete from zirconia is shown in Fig. i. To produce the filler, the foam briquets, made of Zr02 by a method described in [16], were ground in a jaw crusher, and the crushed material was screened into fractions of large and fine fillers.

The suspension was prepared from powdered Zr02 stabilized with 15% (weight parts) Y203, obtained by the combined precipitation of components from solutions of chlorides [ii].

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