The valence state of bismuth in BaBiO3 probed by NQR

We report the NQR on Ba nuclei in four samples of BaBiO 3 prepared in different ways. The spectra of 137 Ba consist of broad line centered near 18 MHz at 4.2 K. The broadening of NQR suggests a local distortions of the crystal structure. The area under the line for ceramic sample BaBiO 3 synthesized at 800°C is approximately two times larger comparing to ceramic samples and single crystal prepared at 930–1080°C. The decrease of the NQR signal is attributed to the partial disordering of charge disproportionating Bi ions on the two inequivalent sites.