Zirconia crystals with yttrium and cerium oxides

Abstract

Results obtained for a new material, namely, zirconia crystals stabilized by Y203 and CeO2 and containing a technological addition of neodymium oxide, tested at room temperature are described. Special features of the surfaces of the crystal blocks grown and the distribution of the additions introduced into the charge over their height are investigated. The dependences of the amounts of the stabilizing components and the fracture properties of the investigated material on its strength are determined. Certification results for the mechanical characteristics of the material are presented (mean four-point bending strength 1250 MPa, crack resistance in bending of a notched bar 11.43 MPa-m ~n at an elasticity modulus of 366 GPa for the crystallographic direction <100>). The crystals are investigated in the crystallographic plane { 100} by applying Vickers and Knoop indenters, and their hardness at different loads (beginning with 0.1 N) is determined. It is established that zones of phase transformations are formed near the indentations in addition to radial and lateral cracks. Problems of change in the specific features of the mechanical behavior of the crystals with change in the valence of cerium (most experiments were conducted for Ce203 ), with the heat treatment, etc. are considered. The results are analyzed using data of fractographic investigations and the new data obtained in tests of similar crystals partially stabilized by yt~ium and terbium oxides.It was established in the early 1980s [1] that crystals of partially stabilized zirconia possess relatively high mechanical parameters and other advantages that make them applicable for various purposes at temperatures up to 1600°C. However, these materials are not used in industry, although a technology for producing coarse crystals with high strength and crack resistance has been devised [2]. This can be explained by the fact that potential users have insufficient information on these crystals and that it is sometimes impossible to prepare materials with uniform structure and properties in an amount sufficient for practical purposes. In growing the crystals it is difficult to eliminate the appearance of cracklike defects, and in long-term storage they sometimes break spontaneously due to internal stresses. This shows that attention to investigating zirconia crystals for structural applications is insufficient. This especially concerns the interdependence of the technological regimes for preparing them, the phase composition, the structure, the laws governing their mechanical behavior, etc. On the whole, data that would make it possible to improve the production technology for these crystals and realize their potentialities are very scarce. As a continuation of previous work in this field [3], we present results of an investigation of crystals whose charge, in addition to zirconia (ZrO 2 ), contained Y203 and CeO 2 plus neodymium oxide 3 (Nd203 ) as a technological addition. These crystals were denoted Y-Ce-PSZ-K.Materials and methods. The experiments were conduct...

Color Evolution in Single Crystal Colored Cubic Zirconias With Annealing Atmosphere and Temperature

“…14) In the case of yellow, BaO and Fe 2 O 3 were confirmed to act as a coloring element. These elements were in agreement with the coloring elements for yellow color reported by Guo et al 15) On the other hand, CeO 2 and Ho 2 O 3 were confirmed to act as a coloring element for red, 16) and Co 2 O 3 and Fe 2 O 3 were contained as a coloring element for purple. In the case of colorless, however, trace amounts of Cr 2 O 3 and TiO 2 were contained in addition to Y 2 O 3 and HfO 2 the essential components of CZs without affecting colors.…”

Indentation resistance of zirconia ceramics and crystals

“…Therefore, for ZrO 2 materials having Z = 1, the coefficients presented in Table 3 are preferable. Note that M and N are approximately equal for ceramics and crystals of the PSZ type (eft 3Y-Ce-PSZ-K with 0.3% CeO2 [31]), which makes it possible to evaluate their crack resistance using one equation with coefficients averaged by the leastsquares method).…”

Влияние валентного состояния ионов Ce на фазовую стабильность и механические свойства кристаллов твердых растворов на основе ZrO-=SUB=-2-=/SUB=-

“…Результаты исследования механических свойств кри-сталлов ЧСЦ, солегированных оксидами иттрия и церия приведены в работах [10,11]. Так, в работе [10] …”