Average and local structure of the Pb-free ferroelectric perovskites(Sr,Sn)TiO3and(Ba,Ca,Sn)

Abstract

Average and local structure of the Pb-free ferroelectric perovskites (Sr,Sn)TiO3 and (Ba,Ca,Sn)TiO3 The characteristic structural off-centering of Pb 2+ in oxides, associated with its 6s 2 lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds Sr0.9Sn0.1TiO3 and Ba0.79Ca0.16Sn0.05TiO3 using neutron total scattering techniques with data acquired at different temperatures. In these compounds, previously reported as ferroelectrics, Sn 2+ appears to display some of the characteristics of Pb 2+ . We compare the local and long-range structures of the Sn 2+ -substituted compositions to the unsubstituted parent compounds SrTiO3 and BaTiO3. We find that even at these small substitution levels, the Sn 2+ lone pairs drive the local ordering behavior, with the local structure of both compounds more similar to the structure of PbTiO3 rather than the parent compounds.

Chemistry, growth kinetics, and epitaxial stabilization of Sn2+ in Sn-doped SrTiO3 using (CH3)6Sn2 tin precursor

“…For example, Sn 2+ located on the A-sites in BaSnO 3 forms an undesirable anti-site defect, whereas a presence of a small a Author to whom correspondence should be addressed. 15,16 Experimental efforts dedicated to the bulk synthesis of Sn-alloyed SrTiO 3 have established that incorporation of Sn 4+ at the Ti-sites can readily be achieved using extreme oxidation conditions, while stabilization of Sn 2+ at the Sr-sites remains highly challenging. 15,[17][18][19] On the other hand, thin-film synthesis approaches offer additional degrees of freedom to tailor the solubility of Sn with epitaxial strain, as well as control over its growth kinetics.…”

Relaxor ferroeletric behavior inSr1−xPrxTiO3:

“…Cubic samples of Sr 1−x Pr x TiO 3 have lower local symmetry, and the AFD instability is greatly enhanced in tetragonal samples. By contrast, the AFD local structure of SrTi 1−x Nb x O 3 is remarkably similar to the long-range phase [32] whereas Sr 1−x Sn x TiO 3 is dominated by the stereochemical lone-pair effect and undergoes a local symmetry decrease only at low temperature [31]. These features make Sr 1−x Pr x TiO 3 more akin to the undoped compound than to other doped SrTiO 3 .…”

“…As a final point, we would like to note that, with respect to other doped SrTiO 3 systems [23,31,32], Pr induces a markedly different structural effect. The first difference concerns the symmetry breaking: Whereas all Ba, Pb [23], or Sn [31] drive the symmetry reduction from P m-3m towards polar space groups, Pr-doped SrTiO 3 mantains the soft-mode phase transition of the undoped material.…”

“…The first difference concerns the symmetry breaking: Whereas all Ba, Pb [23], or Sn [31] drive the symmetry reduction from P m-3m towards polar space groups, Pr-doped SrTiO 3 mantains the soft-mode phase transition of the undoped material. The second difference deals with the relationship between long-range and local structure.…”

Microestrutura e propriedades elétricas e dielétricas do titanato de estrôncio puro e contendo aditivos

“…Muitos estudos sobre as propriedades do SrTiO 3 estão sendo realizados, tais como em propriedades: termoelétricas [27], ópticas [28], ferroelétricas [29] e elétricas [11].…”