On the Solubility of Bi in Tetragonal Tungsten Bronzes
Zeiger, Caren Regine; Williamson, Benjamin Albert Dobson; Walker, Julian Bradley; Einarsrud, Mari-Ann; Grande, Tor
Peer reviewed, Journal article
Published version
Permanent lenke
https://hdl.handle.net/11250/3116799Utgivelsesdato
2024Metadata
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- Institutt for materialteknologi [2544]
- Publikasjoner fra CRIStin - NTNU [37963]
Originalversjon
10.1016/j.jeurceramsoc.2024.01.005Sammendrag
Ferroelectric Pb5Nb10O30 (PN) tetragonal tungsten bronze (TTB) forms solid solutions that exhibit morphotropic phase boundaries (MPBs). Successful replacement of PN with TTBs containing Bi could advance lead-free TTB MPBs. The most studied Bi containing TTB, K4Bi2Nb10O30, was recently demonstrated to be paraelectric, and we have systematically explored the possibility to increase the Bi-content beyond two Bi3+ ions per unit cell aiming to induce ferroelectricity. Higher Bi content was incorporated by either increasing the cation vacancy concentration on the A-site or by B-site substitution with lower valency cations. An additional pyrochlore phase was found in almost all the explored compositions exceeding two Bi3+ per unit cell. The instability of the TTB structure with higher Bi3+ concentrations was investigated in terms of first-principles calculations, combined with chemical considerations and including the tolerance factor. Consequently, an in-plane polarisation found in PN is unlikely to exist in Bi-based TTBs, meaning that Bi3+ cannot fully replace Pb2+ in ferroelectric TTBs.