Sintering of 3 mol % Y2O3-TZP and its fracture after ageing treatment

TZP ceramic of 99.7% theoretical relative final density was obtained by pressureless sintering a commercial co-precipitated 3 mol % Y₂O₃-ZrO₂ powder at 1400° C for 10 h. Fracture surfaces of the aged material revealed that the fracture of TZP ceramic was typified by an intergranular mode in areas where the phase was mainly tetragonal, whereas the transgranular mode was found predominantly in the area containing more monoclinic phase. Microcracks induced by the (t) (m) transformation provided short paths for water to accelerate the property degradation of TZP upon low-temperature ageing in a humid atmosphere.     

Characteristics and sintering behaviour of 3 mol % Y2O3-ZrO2 powders synthesized by reaction in molten salts

Yttria-stabilized tetragonal zirconia powders have been synthesized by reaction in molten salts at 450 °C. To obtain a Y₂O₃-ZrO₂ solid solution powder, it was necessary to use yttrium salts (not yttrium oxide directly) in molten NaNO₃-KNO₃ eutectic. The agglomeration state of the powders depended on their washing conditions. An alcohol-washed powder containing soft agglomerates led to a fine-grained and high-density sintered body.     

Surface nucleation and cellular growth kinetics of cordierite glass ceramics containing 3 mol % Y2O3-ZrO2

Cordierite-based glass ceramics of the 2MgO2Al₂O₃5SiO₂ composition with t-ZrO₂ (3 mol% Y₂O₃-ZrO₂) and P₂O₅ addition, was heat-treated isothermally and isochronically for crystallization studies. Major crystalline phases incurred by the heat treatment were t-ZrO₂ and -cordierite. Surface nucleation predominated when edge and corner nucleation in these samples were suppressed regardless of their radii of curvature. Crystallization began with the formation of -quartz S.S. and its transformation to -cordierite was followed by prolonged heating. Cellular growth of -cordierite on the surface of the quenched glass plates, gave a linear kinetics. The activation energy for cellular growth was 410 kJ mol^–1.     

Optical and electrical properties of laser-irradiated In2O3-4 mol % SnO2

The structural, electrical and optical properties of r.f. sputtered indium-tin oxide films on fused silica substrates and laser-treated films in air were investigated. The transmittance in the visible range was increased and the electrical resistivity was decreased by the laser treatment. The laser treatment was also found to annihilate dislocations and to promote grain growth. The improvement in these optical and electrical properties may be mainly due to the annihilation of defects such as vacancies and interstitials.     

Rapid Solidification of ZrO2–8 mol % Y2O3 Melt under Conditions of Stepwise Reduction of Heating. Determination of the Liquidus and Solidus Temperatures

Investigations are conducted into the process of crystallization of a bath with a ZrO₂–8 mol % Y₂O₃ melt which is produced by local heating of ceramic by concentrated laser radiation and solidifies when the radiation power decreases by 20–30%. It is demonstrated that a gently sloping temperature plateau is observed in the process of solidification, which may be used to estimate the liquidus temperature.     

Electrical conductivity of Cr2O3-doped Y2O3-stabilized ZrO2

The electrical conductivity of Cr₂O₃-doped Y₂O₃-stabilized ZrO₂ (YSZ) has been studied as functions of composition, temperature and oxygen pressure. The specimens have been prepared by hot preoning of co precipitated oxides to yield >99.7% density. The Cr₂O₃ added above the solubility limit ( 0.7 mol %) precipitated as a secondary phase at the grain boundaries. The conductivity of Cr₂O₃-doped YSZ was almost independent of the oxygen pressure in the range 10¹⁸ to 10⁵ Pa, indicating a dominant ionic condition. The electronic conductivity of dopant CR₂O₃ would be hindered by the higher ionic conductivity in thep _O2 ranges studied. The conductivity and the activation energy for conduction decreased slightly with the addition of Cr₂O₃. These phenomena seemed to be caused by vacancy trapping or polarization at the grain boundaries with the Cr₂O₃ precipitates. The samples with 1 mol % Cr₂O₃ addred to zirconia containing various Y₂O₃ contents showed similar conduction behaviour to those without Cr₂O₃ addition; that is, the conductivity maxima are observed at around 8 mol % Y₂O₃ addition to zirconia, and the activation energies increased with tha Y₂O₃ addition.