RARE “Discovered Ferroelectricity" Dr Joseph Valasek Signed 3X5 Card COA For Sale

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RARE “Discovered Ferroelectricity" Dr Joseph Valasek Signed 3X5 Card COA:
$399.99

Up for sale "Ferroelectricity" Joseph Valasek Hand Signed 3X5 Card. 

ES-7293E

When

a PhD student called Joseph Valasek discovered ferroelectricity exactly 100

years ago, few people realized the enormous impact it would have on science and

technology. Amar S Bhalla and Avadh Saxena pick their favourite applications of this fundamental physics

phenomenon. Great discoveries are sometimes made without anyone

realizing quite how important they will be. C V Raman,

for example, won the Nobel Prize for Physics in 1930 for discovering that light

can change energy when it scatters, yet Raman spectroscopy did not become a

valuable research tool until well after the laser was invented in 1960.

Similarly, few could have imagined that Paul Dirac’s

far-fetched yet bold proposal of antiparticles – for which he won the 1933

Nobel prize – would lead to positron emission tomography half a century later. But

there is a lesser known – yet important – discovery that also went largely

unrecognized at the time. It was made 100 years ago in 1920 by Joseph Valasek

(1897–1993), who was then a graduate student working under the supervision of

William Swann at the University of Minnesota, Minneapolis, US. Seeking to

develop a seismograph to measure the vibrations from earthquakes, Valasek

wondered if this could be done with piezoelectric crystals, which create an

electric signal when squeezed. The most readily available piezoelectric he had

at hand was a single-crystalline substance first synthesized in the 17th

century by Pierre Seignette, a pharmacist from the French seaport of La

Rochelle. Extracted from wine, it became known as Rochelle salt or Seignette

salt and has the chemical formula potassium sodium tartrate tetrahydrate (KNaC4H4O6·4H2O).

When Valasek placed a sample of this material in an electric field, E,

he noticed that its resulting electric polarization, P, did

something unusual. As he turned up the field, the polarization increased,

with the graph of P versus E following an

S-shaped curve. However, when the field was lowered again, the polarization was

always higher than before albeit following the same kind of curve. In other

words, the precise value of the polarization depended on whether the field was

rising or falling: it was showing hysteresis (figure 1). So unusual was this

observation that Swann presented it at the April 1920 meeting of the American

Physical Society in Gaithersburg, Maryland, in a paper entitled “Piezoelectric

and allied phenomena in Rochelle salt”. (As a lowly PhD student,

Valasek did not even attend the meeting.) Swann and Valasek did not know

what caused the hysteresis, but there were parallels with a discovery that had

been made three decades earlier by the Scottish physicist James Alfred Ewing.

He had seen a similar kind of behaviour in certain ferromagnets, noticing that

the magnetic moment depends on how the magnetic field has changed. Valasek’s

discovery therefore pointed to an entirely new class of materials, in which the

electric dipole moment – and hence the polarization – depends on how the

electric field has changed.

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RARE “Discovered Ferroelectricity" Dr Joseph Valasek Hand Signed 3X5 Card COA

$399.99

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