LIVXNB1-XO3 (X-LESS-THAN-OR-EQUAL-TO-0.2) AND LI2VNBO6 PHASES PREPARED BY HIGH-PRESSURE AND HIGH-TEMPERATURE SYNTHESIS

This study reports structural variations, investigated with X-ray diff raction and vibrational spectroscopy, in new LiNbO3-LiVO3 compounds ob tained through synthesis at high pressure (9 GPa) and high temperature (873K). X-ray diffraction reveals the existence of the LiNbO3-LiV0.2N b0.8O3 solid solution and Li2VNbO6 partially ordered phase. Optical ph onons are examined in relation to changes in composition of the synthe sized materials. Ordering, as evidenced by Raman spectroscopy, leads t o local vibrational modes observed in the high frequency region with p redominant cation-oxygen stretching modes. These local vibrational mod es can be interpreted as being due to various disorder-partial order m icrodomains or impurities with other ordering schemes. (C) 1997 Elsevi er Science Ltd. All rights reserved.