Nuclear quadrupole resonance of barium in BaBiO3 and BaPbO3 - art. no. 184106

The nuclear quadrupole resonance (NQR) on Ba nuclei was studied in four sam ples of BaBiO3 prepared in different ways and, in addition, in BaPbO3. The spectrum of Ba-137 at T = 4.2 K consists of a relatively broad line centere d near 18 MHz for all BaBiO3 samples and near 13 MHz for BaPbO3. The integr ated intensity of the Ba-137 resonance in the ceramic sample of BaBiO3 synt hesized at 800 degreesC is approximately twice as large as that in ceramic samples and a single crystal prepared at 930-1080 degreesC. The decrease of the NQR signal can be attributed to the partial disordering of charge-disp roportionated Bi ions on the two inequivalent sites. The broadening of the resonance indicates that local distortions of the crystal structure exist i n both compounds. The point-charge model was used to analyze the electric-f ield gradient on the Ba sites.