Effects of Noncompositional Inhomogeneity on t→m Phase Transformation During Grinding of Various Rare‐Earth‐Doped Zirconias

Masatomo Yashima, Tatsuo Noma, Nobuo Ishizawa, Masahiro Yoshimura

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The phase transformation from metastable tetragonal (t) into monoclinic (m) phase must be studied using samples that are homogeneous in their compositions and microstructures. The present study investigated the transformability by grinding for compositionally homogeneous samples prepared by rapid quenching of melts in the system ZrO2–RO1.5 (R: Nd, Sm, Y, Er, Yb). The volume fraction of m‐phase Vm(tg) against grinding time tg was investigated using powder X‐ray diffraction for the rapidly quenched sample. The Vm(tg) value increased with grinding time tg, then saturated to a certain value Vm(∞) of between 1 and 0 when it was ground and crushed for a long time. Both the transformation rate (dVm/dtg)tg = 0 and the saturated value Vm(∞) decreased with dopant content X. The species of dopants had less influence on the transformability. The experimental Vm(∞) and Vm(0) data could be explained using a model which has a normal distribution of effective free energy change between t and m phases, ΔGt‐m, among hypothetical parts of the sample. This distribution occurred because of nonchemical energies such as strain, interfacial, and surface energies, which associated with the nucleation of m phase. The average effective free energy change ΔG¯t‐m/σ was found to be a linear function of ErO1.5 content X as 0.65X+ 3.00, where σ is a standard deviation of the normal distribution. The transformation rate dVm/dtg at tg= 0 decreased with RO1.5 content. The axial ratio c/a of the t phase was an important factor in the transformability, the Vm(0), Vm(∞), and the dVm/dtg. The validity and limitation that the c/a is a factor of the transformability were discussed.

Original languageEnglish
Pages (from-to)3011-3016
Number of pages6
JournalJournal of the American Ceramic Society
Volume74
Issue number12
DOIs
Publication statusPublished - 1991 Dec

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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