High-pressure studies have shown that $\mathrm{K}{\mathrm{Ta}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ crystals with small $x(\approx 0.02)$ exhibit relaxational glasslike behavior rather than a static ferroelectric structural phase transition as previously thought. The results show a pressure-induced transition from frozen to relaxing impurity behavior and evidence for an off-center to on-center transition of the Nb ion at the $B$ site of the perovskite lattice.

• Received 7 May 1984

DOI:https://doi.org/10.1103/PhysRevLett.53.298