Electrical and spectroscopic investigations of phase transitions in ferroelectric TAAP and DTAAP

Abstract

(1) TAAP and DTAAP show pronounced anomalies in dielectric constant at TcT_cTc? and follow Curie–Weiss law in both ferro? and paraelectric phases. (2) The dielectric constant and coercive field values of TAAP depend on the thickness of the sample. (3) Dielectric relaxation of TAAP near Curie temperature suggests that the phase transition in this crystal is of order–disorder type. (4) Deuteration of TAAP increases the transition temperature from 45° to 87?°C indicating the importance of hydrogen bonds. (5) Pyroelectric measurements show that DTAAP exhibits higher value of pyroelectric coefficient at TcT_cTc? than TAAP. In conclusion the following facts have been established from the above switching studies and irradiation effects on TAAP and DTAAP:

The switching process in TAAP is slower than in TGS and of DTAAP slower than TAAP.

The switching process in this crystal is predominantly governed by a linear forward growth process for the range of fields employed.

X?ray irradiation causes an increase in the threshold field below which the switching does not occur and decreases the dynamic mobility.

Irradiation increases the value of coercive field.

TAAP crystals have different domain structures of both predominantly single and multi?domains, depending on which the internal bias increases or remains unaffected upon irradiation.

Irradiation decreases the peak value of the dielectric constant and also the transition temperature.