Phase evolution in reaction sintered zirconium titanate based materials

Abstract

Zirconium titanate materials are proposed for structural components for which fully reacted and relatively large pieces are required. In this work the phase evolution in slip cast compacts constituted by equimolar mixtures of TiO 2 and ZrO 2 stabilized with 3 mol% of Y 2 O 3 at high temperature is studied, to establish the basis to design suitable thermal treatments for ZrO 2 (Y 2 O 3 )-TiO 2 materials. The temperatures at which the processes involved in the reaction sintering occurred were identified by constant heating rate experiments. Phase and microstructure analyses have been performed on specimens treated at the identified temperatures and air quenched. Then the adequate temperature range to get fully reacted and dense materials has been deduced. Materials treated at 1500 • C to 2 h were constituted by Zr 5 Ti 7 O 24 as major phase, a solid solution of TiO 2 and Y 2 O 3 in c-ZrO 2 as secondary phase and a ZrO 2 -TiO 2 -Y 2 O 3 non-stoichiometric compound with pyrochlore structure as minor phase. Pyrochlore was demonstrated to be a metastable phase at 1500 • C.

Dispersion of mixtures of submicrometer and nanometre sized titanias to obtain porous bodies

“…The shrinkage curve of submicrometer sized titania (Merck), reported in a previous work [37] showed two significant slope changes that were highlighted in the derivative curve (Figure 6a). The first one, occurring at about 1060 ºC was identified as the transformation of anatase to rutile, which involves a sudden shrinkage of about 8.5 vol.% (calculated using the theoretical densities of anatase−TiO 2 , 3.89 g/cm 3 , and rutile-TiO 2 , 4.25 g/cm 3 ).…”

Titanato de circonio: estabilidad termodinámica y expansión térmica

“…Los métodos sol-gel [28], permiten obtener ZrTiO 4 por tratamiento térmico a temperaturas de 500-600°C. La mayoría de los trabajos describen métodos de fabricación de polvos o piezas pequeñas, no habiéndose descrito la fabricación de piezas masivas (≈ 60 x 60 x 5 mm 3 ) hasta fecha reciente [29][30][31].…”

“…En 2010 López-López y col. [31] estudiaron mezclas equimolares de TiO 2 y t-ZrO 2 estabilizada con 3% mol de Y 2 O 3 calentadas a 1500ºC durante 2 y 30 horas con velocidades de calentamiento y enfriamiento de 5ºC/min. Encontraron un compuesto con estructura pirocloro en los bordes de grano de ZrTiO 4 y c-ZrO 2 ss en los materiales tratados durante 2 horas.…”

“…Si se representan en un diagrama ternario los puntos experimentales estudiados por McHale y Roth [4], Colomer y col. [46], Kobayashi y col. [48], Feighery y col. [49], Schaedler y col. [50] y López-López y col. [31] (Fig. 11.…”

“…11) y Schaedler y col. [50] (30 % mol ZrO 2 , 50 % mol TiO 2 , 20 % mol YO 1.5 y 40 % mol ZrO 2 , 50 % mol TiO 2 , 10 % mol YO 1.5 , puntos 3 y 4, respectivamente en la fig. 11) que estarían en una región trifásica de ZrTiO 4 ss, c-ZrO 2 ss y TiO 2 ss, y con el punto experimental estudiado por López-López y col. [31] (47.78 % mol ZrO 2 , 49.26 % mol TiO 2 , 2.96 % mol YO 1.5 , punto 5 en la fig. 11) el cual estaría en una región bifásica de ZrTiO 4 ss y c-ZrO 2 ss.…”