Elastic constants C(ii) (i=1 to 6) are investigated by Brillouin scatt
ering from room temperature up to 130-degrees-C including the ferroele
ctric transition near 97.5-degrees-C. Small anomalies are observed for
C-11, C22 and C33 near that transition. The results are discussed in
terms of piezoelectric, electrostrictive and higher order couplings.