The penetration depth in several hard superconductors

Abstract

The present work reports the elaboration and physical investigation of new compounds of the following composition Ba1−xNax(Ti1−ySny)1−xNbxO3 (BTSnNxy). The studied ternary system presents some continuous solid solutions between the next 3 phases: the NaNbO3 antiferroelectric phase that becomes easily ferroelectric at low rate substitutions, the BaTiO3 ferroelectric phase and the paraelectric stannate phase BaSnO3. Two different dielectric behaviors can be observed once some substitutions are made either in A or B sites of an ABO3 perovskite. These substitutions modify the dielectric properties of the material. The introduction of Sn4+ and Ti4+ cations in the B site favors, respectively, a decrease of the transition temperature and an increase in the value of the real dielectric permittivity. The transition temperature should be modulated by varying the rate of cationic substitution. Some relaxor materials can be obtained at a temperature around room temperature.