The valence state of bismuth in BaBiO3 probed by NQR

Authors report the NQR on Ba nuclei in four samples of BaBiO3 prepared in different ways. The spectra of 137Ba 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 BaBiO3 synthesized at 800 C is approximately two times larger compared with 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. 8 refs.