Ca4Nb209-CaTi03: Phase Equilibria and Microstructures

Published

August 1, 2001

Author(s)

Leonid A. Bendersky, Igor Levin, Robert S. Roth, Alexander J. Shapiro

Abstract

Ca₄TiO₃-Ca₄Nb₂O₉ is a quasi-binary section, and all the phases participating in equilibrium are solid solutions of the binary end-members. The phases are perovskite-based ABO3-type, with a common stoichiometry Ca[Ca_(1-x)/(3-2x)Nb_{(2-2x)/ (3-2x)}Ti_x/(3-2x)]O3. The differences between the lower- temperature phases is in the type of ordering between Ca/Nb/Ti ions occupying the B-site, as well as in the type of octahedral tilting. The proposed phase diagram has the following single-phase fields: (1) cubic disordered C (Pm3m), (2) a series of disordered CaTiO₃-type polymorphs T, O₁ and O₂(Pnma) with different combination of tilting; (3) low-Ti disordered/tilted O'₂(Pnma); (4) 1:1 ordered/tilted HTP₂; (4) 1:2 ordered/tilted LT_1/6. The single-phase fields are connected with the following reactions of the phases: (1) high-temperature monotectoid C ->C'+O'₂; (2) miscibility gap C'+C; (3) eutectoid HTP₂->LT_1/6+O₂; (4) a series of peritectoid reaction between O'2 and CaTiO₃ polymorphs; (5) an ordering transition O'₂->HTP₂. In addition, a metastable transition to the 1:3 ordered LT_1/4 phase occurs for a wide range of compositions (0

Citation

Journal of Solid State Chemistry

Volume

160

Issue

No. 1

Pub Type

Journals

Keywords

CaTi0₃-Ca₄Nb₂0₉, dielectrics, phase diagram, TEM

Citation

Bendersky, L. , Levin, I. , Roth, R. and Shapiro, A. (2001), Ca₄Nb₂0₉-CaTi0₃: Phase Equilibria and Microstructures, Journal of Solid State Chemistry (Accessed October 13, 2024)