Elastic and piezoelectric properties of MAPCB crystals have been studi
ed in the temperature range 110 to 310 K. A correlation between change
s in the elastic properties and anomalies in the spontaneous polarizat
ion of the crystals at 170 K is found. No anomaly in the piezoelectric
properties in the vicinity of the newly postulated phase transition a
t 250 K has been detected.