Ferroelectricity Lab Report

The main feature of ferroelectricity is the polarization reversal (switching) with electric field. This can be observed by measuring the polarization vs electric field hysteresis loop (P-E hysteresis loop). This is usually done by using Sawyer-Tower circuit [17] as shown in Figure 2.10. An alternating voltage V is applied across the electrodes on the ferroelectric material and a capacitor Co with high value of capacitance is connected in series with the test sample (C_x) and then studying the relationship between the stored charge and the instantaneous voltage for test sample. The voltage across this capacitor measures the charge stored in the test sample. Figure 2.10 Diagram of Modified Sawyer-Tawer Circuit For the present work, the

The piezoelectric coefficient is defined by charge generated per unit force both in the direction of polarization of piezoelectric material. The piezoelectric charge coefficient is given using relation: d_33=Q/F =CV/F …………………..2.18

Where Q=CV is the charge developed per unit electrode area of piezoelectric material, C is the capacitance, V is the Voltage and F is the force applied in Newton (N).

Piezoelectric coefficient can be measured by different methods- (1) Static Method (2) Quasistatic Method (3) Resonance

The ME effect in composite is a result of the interaction of magnetic and piezoelectric phases through strain – stress coupling. ME voltage coefficient depends on mechanical coupling, resistivity and molar ratio of constituent phases and applied DC magnetic field. ME coefficient was measured in terms of variation of the change in electric field with respect to change in magnetic field as a function of dc magnetic bias field. ME characterization in the ceramic was studied by measuring the voltage response of the ceramic subjected to alternating and constant (bias) magnetic field. The bias magnetic field (Hdc) was obtained using an electromagnet and the alternating magnetic field was generated by Helmboltz coil. ME effect was characterized by a ME voltage coefficient α which is given by [19]. α=V/(H_ac ×d) ……………….2.19

Where V is the voltage generated due to magneto electric effect, Hac is the amplitude of alternating magnetic field and d is the thickness of the