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Piezoelectric property distribution was investigated in a Pb(Mg 1/3 Nb 2/3 ) 0.7 Ti 0.3 O 3 single-crystal (001) wafer grown by the Bridgman technique. There are three visual areas in the crystal: opaque part, transparent part and dendritic part. The piezoelectric properties of the dendritic part were similar to those of the transparent part, and the electromechanical ( e / m ) coupling coefficient of the length mode, k 31 was 70.6% at -25°C and increased to its highest value of 84.6% at 68°C. The e / m coupling factors of the thickness mode k t (59–60%) were almost the same in the transparent part and opaque part at room temperature. However, there was a large difference in k 31 between the transparent part ( k 31 =76%) and the opaque part ( k 31 =51–60%). Therefore, k 31 measurement is a good tool for determining the quality and uniformity level of Pb(Mg 1/3 Nb 2/3 ) 1- x Ti x O 3 single crystals.
Karaki et al. (2002) studied this question.