SECOND ORDER PHASE TRANSITIONS AS STUDIED BY REAL TIME TRANSMISSION, DIFFRACTION AND SANS G.M.Mironova, Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
Previously/1,2/ it was announced about the observation of the thermal shock induced phase transitions in different materials using real time neutron scattering technique developed for the last years at the IBR-2 reactor on the DN-2 diffractometer in Dubna/3/. Due to short accumulation of spectra (several sec for powder samples), it is possible to follow evolution of atomic structure over a momentum transfer range 0.001-10 Å-1 while heating and cooling with the rates of 1-20 K/min and more. Addition of transmission channel/4/ permits one to complete the information from the sample. Such a technique was applied for the investigation of the second order phase transitions in quartz (alpha-beta), iron (alpha-gamma) and Y-based HTSC (ortho-tetra). It was found, that all these transitions may be induced by the thermal shock, and the materials remember such events. As to phase transitions in true thermodynamical points, quite new information about scenario was received. All the data may be understood from the single point of view being controversial to modern considerations.
1G.M.Mironova, French-Russian Seminar, Col de Porte, Grenoble, France, March 23-28, 1995.
2G.M.Mironova, A.M.Balagurov, Annual Report FLNP, 1995, Dubna.
3G.M.Mironova, Materials Science Forum v.79-82 (1991) 487.
4G.M.Mironova, Annual Report FLNP,1995, Dubna.