Size effect in isometric PbTiO3 crystals

The phase transitions Pm3m⇄P4mm and domain-structure formation in 5–500 μm isometric PbTiO₃ crystals were investigated. The phase transition is characterized by a high rate and by the formation of a single flat interphase boundary {023}. A size effect was observed: In crystals smaller than a critical size (about 20 μm), formation of 90° domains stops and, in agreement with a phenomenological theory, the temperature hysteresis of the phase transition doubles. Fiz. Tverd. Tela (St. Petersburg) 40, 1546–1547 (August 1998)     

K-groups of multidimensional local fields

Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 41, No. 2, pp. 266–268, February, 1989.     

A novel convenient synthesis of 5-acyl-1,2-dihydropyrimidin-2-ones via 4-trichloromethyl-1,2,3,4-tetrahydropyrimidin-2-ones

A novel four-step methodology for the synthesis of 5-acyl-1,2-dihydropyrimidin-2-ones has been developed. The reaction of readily available N-[(1-acetoxy-2,2,2-trichloro)ethyl]ureas with Na-enolates of 1,3-diketones or β-oxoesters followed by heterocyclization-dehydration of the oxoalkylureas formed gave 5-acyl-4-trichloromethyl-1,2,3,4-tetrahydropyrimidin-2-ones. The latter, in the presence of NaH, eliminate CHCl₃ to give the target compounds.     

Polarization switching in metal-dielectric-metal structures with polycrystalline and heteroepitaxial (Ba,Sr) TiO3 films produced by cathode sputtering

The characteristics of polarization switching are studied in metal-dielectric-metal structures as the basis of (Ba, Sr)TiO₃ films having a different degree of crystal lattice perfection. The relationships discovered support the conclusions of a phenomenological model of the spreading of the ferroelectric phase transition, according to which microvolumes of the film material are distributed by the magnitude of deformation (the sum of spontaneous deformation and induced defects) and, consequently, by the magnitude of the spontaneous polarization, Curie temperature, coercive field, etc., while the half-width of this distribution is a measure of the average microdefect. The experimentally obtained results show that the items studied have promising applications in active and permanent computer memory devices.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 28–31, April, 1986.