Matsayin Kayayyakin Ferroelectric: Me Sune?

Me kowane su Ferroelectric Materials?

Ferroelectric materials suna da suke cikin yadda suke da Ferroelectricity. Ferroelectricity yana nufin yadda zai iya samun electric polarization daga rikita. Wannan polarization zai iya canzawa ta hanyar amfani da electric field a kan waje (takarda 1 a nan). Ferroelectricity (kuma don haka Ferroelectric materials) an samu shi a shekarar 1921 ta hanyar Valasek.

Canzawar polarity na ferroelectric material ta hanyar amfani da electric field na musamman ya ce “switching”.

Ferroelectric materials zai iya taimaka da polarisation har sai ba a ci gaba a kan electric field. Ferroelectric materials suna da wasu taswirwa a kan ferromagnetic materials, wadanda suka fitowa permanent magnetic moment. Hysteresis loop ana cikin wasu abubuwan da suka da ita a kan duk waɗannan abubuwa.

Saboda akwai wasu taswirwa, prefix ya sama a kan duk waɗannan abubuwa. Amma babu duk ferroelectric material ya zama da Ferro (iron).

Duk ferroelectric materials suna da piezoelectric effect. Wasu abubuwan da suka fi shi a kan antiferromagnetic materials.

Theory of Ferroelectric Materials

Free energy na ferroelectric material ta hanyar Ginburg-Landau theory saboda ba da electric field ko applied stress zai iya rubuta a hanyar Taylor expansion. An rubuta shi a kan P (order parameter) kamar yadda ake bayyana a nan.

(idance sixth-order expansion an amfani)
Px → component of polarization vector, x
Py → component of polarization vector, y
Pz → component of polarization vector, z
αi, αij, αijk → coefficients should be constant with the crystal symmetry.
α0 > 0, α111> 0 → for all ferroelectrics
α11< 0 → ferroelectrics with the first-order transition
α0 > 0 → ferroelectrics with second-order transition

Don in bincike wasu abubuwa da domain formation a cikin ferroelectrics, wannan equation suke amfani a cikin phase-field model.

Yanzu, an amfani shi ta hanyar hada tsari kamar elastic term, gradient term, da electrostatic term zuwa wannan free energy equation.

An halarta equations using finite difference method, subject to Linear elasticity and Gauss’s law constraints.

Cubic to tetragonal phase transition of spontaneous polarization of a ferroelectric zai iya samu shi daga expression for free energy.

It has a character of dual well potential with double energy minima at P = ± Ps.
Ps → spontaneous polarization

By simplifying, eliminating the negative root, and substitute α11 = 0 we get,

Polarization and Hysteresis Loop

First, we take a dielectric material, and a peripheral electric field is given. We can see that the polarization will always be directly proportional to the applied field, represented in figure 2.

Next, when we polarise a paraelectric material, we get a nonlinear polarization. However, it is a function of the field, as shown in figure 3.

Next, we take a ferroelectric material, and an electric field is given to it. We get a nonlinear polarization.

It also exhibits nonzero spontaneous polarization without a peripheral field.

We can also see that by inverting the direction of the applied electrical field, the direction of polarization can be inverted or changed.

Thus, we can say that the polarization will depend on the present and the previous condition of the electric field. The hysteresis loop is obtained as in figure 4.

Curie Temperature

The properties of these materials exist only below a definite phase conversion temperature. Above this temperature, the material will become paraelectric materials.

That is, loss in spontaneous polarization. This definite temperature is called Curie temperature (T