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2.3 Ostsillografichesky method - definitions of spontaneous polarisation

The given method has been featured for the first time in Sawyer's operation and Tauera in 1930 [142]. The ferroelectric loop of the dielectric hysteresis is easy for observing on the oscillograph screen.

Loops of the dielectric hysteresis represent dependence of electrical polarisation on intensity of an exterior electric field, are one of the basic performances of any ferroelectric material. On them it is possible to spot spontaneous Pc (and-or residual Poc τ) polarisation. The key diagramme of this method is presented on fig. 2.9. The Alternating voltage from the generator or the transformer moves on joined consistently explored sample of a ferroelectric material (emkostjui calibration capacitor Set.

Voltage [D with reference kondensatorapodayotsja on inlet Y

Oscillograph. This voltage is proportional to a charge qна a calibration capacitor. A charge qможно to spot from a relation

Where Ux - a voltage on the sample. As a charge qсвязан with a surface density of a charge and a relation

Where S' - a surface area of the sample in a case when the vector of polarisation R is perpendicular crystal surfaces, we have

Substituting (2.12) and (2.11) in (2.13), we gain for polarisation

From here follows, that the voltage on calibration capacitor Uпрямо is proportional to River polarisation

On an inlet of X oscillograph the voltage from a ferroelectric crystal moves (at use in experiment of major quantity of an electric intensity the divider consisting from two is applied

Consistently joined resistances R1и R2), proportional to quantity of the electric field enclosed to the sample.

Fig. 2.9. The plan for observation of loops of the dielectric hysteresis

Thus, on the oscillograph screen (at the ungeared scanning generator of a horisontal deflection) it is possible to see the hysteresis curve image q ^q (u) - dependence of a charge q (or polarisation P = q/S) from voltage Uxна its plates (or electric intensity E = UJd, where d - a thickness of the sample). The given method allows to measure both quantity of polarisation of a ferroelectric material, and a coercive field.

In too time, the given method does not allow to spot the full value of spontaneous polarisation in ferroelectric materials, which owing to structural features have fields (termed as clusters) with not switched polarisation. In these cases on an oscillograph, even in case of the "opened" loop of the dielectric hysteresis, switched polarisation is observed not spontaneous, but. To the materials possessing similar properties, monocrystals of firm solutions explored in operation niobata barium of strontium SrxBa1.xNb2θ6 and niobata barium of calcium CaxBa1.xNb2θ6 concern.

In experiment of a loop of the dielectric hysteresis were fixed by means of a numeral photographic camera, and then were handled on the computer.

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A source: Lisitsyn Vladimir Sergeevich. PYROELECTRIC PROPERTIES And the STATE of POLARIZATION of MONOCRYSTALS of FIRM SOLUTIONS NIOBATA of BARIUM of STRONTIUM And NIOBATA CALCIUM BARIUM. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Tver - 2015. 2015

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  2. the effects related to shielding of spontaneous polarisation
  3. 1.4. Influence of spontaneous polarisation on properties of the interface stratums in a sheet ferroelectric material
  4. 2.2. The analysis of a state of polarisation in segnetoaktivnyh materials with use TSW of a method
  5. 4.4 Examination of polarisation by a method of loops of the dielectric hysteresis.
  6. 4.2 Examination of a self-polarised state and local polarisation of thin films TSTS by a method of power microscopy of the piezoelectric response.
  7. the Spontaneous attack supported by interested persons
  8. Spontaneous information attacks.
  9. § 1.2. Spontaneous regulation of protection of cultural values.
  10. the analysis pirootklika double-layer ferroelectric structures with opposite value of polarisation
  11. temperature dependences of residual polarisation
  12. Self-polarisation in films of a ferroelectric material
  13. a lateral view of polarisation of schistose structures on the basis of BTS
  14. 4.1. Influence of a temperature cycling on a state of polarisation of crystals SBN
  15. influence of exterior actions on a state of polarisation of crystals CBN