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Ca4Nb209-CaTi03: Phase Equilibria and Microstructures



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


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)Tix/(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 LT1/6. 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->LT1/6+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 LT1/4 phase occurs for a wide range of compositions (0
Journal of Solid State Chemistry
No. 1


CaTi0<sub>3</sub>-Ca<sub>4</sub>Nb<sub>2</sub>0<sub>9</sub>, dielectrics, phase diagram, TEM


Bendersky, L. , Levin, I. , Roth, R. and Shapiro, A. (2001), Ca<sub>4</sub>Nb<sub>2</sub>0<sub>9</sub>-CaTi0<sub>3</sub>: Phase Equilibria and Microstructures, Journal of Solid State Chemistry (Accessed February 26, 2024)
Created August 1, 2001, Updated February 17, 2017