Piezoelectric Effect (Marie Curie, Pierre Curie)

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Piezoelectric Effect (Marie Curie, Pierre Curie)

Curie, Marie (1867-1934) or Curie, Pierre (1859-1906), French physicists and Nobel laureates, who were wife and husband; together, they discovered the chemical elements radium and polonium. The Curies' study of radioactive elements contributed to the understanding of atoms on which modern nuclear physics is based.
Pierre Curie was born in Paris on May 15, 1859, and studied science at the Sorbonne. In 1880 he and his brother Jacques observed that an electric potential is produced when pressure is exerted on a quartz crystal. The brothers named the phenomenon piezoelectricity. In the course of later studies of magnetism, Pierre Curie discovered a certain temperature (the Curie point) at which magnetic substances lose their magnetism. In 1895 he was named professor in the School of Physics and Chemistry in Paris.
Originally named Marja Sklodowska, Marie Curie was born in Warsaw on November 7, 1867. Her father taught high school physics. In 1891 she went to Paris (where she changed her name to Marie) and enrolled in the Sorbonne. Two years later she passed the examination for her degree in physics, ranking in first place. She met Pierre Curie in 1894, and they married in 1895.
Marie Curie was interested in the recent discoveries of radiation. Wilhelm Roentgen had discovered X rays in 1895, and in 1896 Antoine Henri Becquerel had discovered that the element uranium gives off similar invisible radiations. Curie thus began studying uranium radiations, and, using piezoelectric techniques devised by her husband, carefully measured the radiations in pitchblende, an ore containing uranium. When she found that the radiations from the ore were more intense than those from uranium itself, she realized that unknown elements, even more radioactive than uranium, must be present. Marie Curie was the first to use the term radioactive to describe elements that give off radiations as their nuclei break down.
Pierre Curie ended his own work on magnetism to join his wife's research, and in 1898 the Curies announced their discovery of two new elements: polonium (named by Marie in honour of Poland) and radium. During the next four years the Curies, working in a leaky wooden shed, processed a ton of pitchblende, laboriously isolating from it a fraction of a gram of radium. They shared the 1903 Nobel Prize in physics with Becquerel for the discovery of radioactive elements.

Marie Curie was the first female recipient of a Nobel Prize.
In 1904 Pierre Curie was appointed professor of physics at the University of Paris, and in 1905 he was named a member of the French Academy. Women not then commonly held such positions, and Marie was not similarly recognized. Pierre's life ended on April 19, 1906, when he was run over by a horse-drawn cart. His wife took over his classes and continued her own research. In 1911 she received an unprecedented second Nobel Prize, this time in chemistry, for her work on radium and radium compounds. She became head of the Paris Institute of Radium in 1914 and helped found the Curie Institute. Marie Curie's final illness was diagnosed as pernicious anaemia, caused by overexposure to radiation. She died in Haute Savoie on July 4, 1934.
The Curies had two daughters, one of whom was also a Nobel Prize winner. Irene Joliot-Curie and her husband, Frédéric, received the 1935 Nobel Prize in chemistry for the synthesis of new radioactive elements.

Piezoelectric Effect, appearance of an electric potential across certain faces of a crystal when it is subjected to mechanical pressure. Conversely, when an electric field is applied on certain faces of the crystal, the crystal undergoes mechanical distortion. Pierre Curie and his brother Jacques discovered the phenomenon in quartz and Rochelle salt in 1880 and named the effect piezoelectricity (from Greek piezein, “to press”).
The piezoelectric effect occurs in several crystalline substances, such as barium titanate and tourmaline. The effect is explained by the displacement of ions in crystals that have a nonsymmetrical unit cell, the simplest polyhedron that makes up the crystal structure. When the crystal is compressed, the ions in each unit cell are displaced, causing the electric polarization of the unit cell. Because of the regularity of crystalline structure, these effects accumulate, causing the appearance of an electric potential difference between certain faces of the crystal. When an external electric field is applied to the crystal, electrostatic forces, resulting in the mechanical deformation of the whole crystal, displace the ions in each unit cell. Because of their capacity to convert mechanical deformation into electric voltages, and electric voltages into mechanical motion, piezoelectric crystals are used in such devices as the transducer, record-playing pickup elements, and the microphone. Piezoelectric crystals are also used as resonators in electronic oscillators and high-frequency amplifiers, because the mechanical resonance frequency of adequately cut crystals is stable and well defined.

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