Cation distribution and piezoelectric properties of aluminum substituted La3Ta0.5Ga5.5O14 single crystals

We report the structure and electric properties of La 3 Ta 0.5 Ga 5.5-x Al x O 14 (LTGAx,x = 0.0 (LTG), 0.3 and 0.5) single crystals, with a Ca 3 Ga 2 Ge 4 O 14 -type structure, suitable for high temperature piezoelectric application. A single-crystal X-ray structure analysis reveals that Al atoms are distributed in all cation sites except for the decahedral site occupied by La, which favors instead the octahedral site. The piezoelectric moduli d 11 kept a constant, whereas [d 14 ] increased 14% with the increasing Al content, x, up to 0.5. The LTGA0.5 crystals showed a low temperature dependence (2% deviation from room temperature to 400°C) of d 11 and a higher electric resistivity p than those of the LTG crystals. The Al substitution is effective for improving the electrical properties of the LTG.