Competing structural instabilities in Bi2SiO5

Bi${}_{2}$SiO${}_{5}$ recently emerged as a promising ambient-temperature lead-free ferroelectric with a Curie temperature of 663 K, where the ferroelectricity arises from the tilt of quasi-one-dimensional SiO${}_{4}$ chains. Here, the authors analyze the competition between ferroelectric and antiferroelectric instabilities by investigating the characteristic temperature-dependent phonon energies at the center and the edge of the Brillouin zone, respectively. The direct evidence for this competition opens the way towards tuning the properties of Bi${}_{2}$SiO${}_{5}$ by application of pressure or electrical field.