Cerâmicas à base de titanato de bário (BaTiO3) dopadas com 0,4% em mol de La e 150 ppm de Mn foram investigadas por microscopia de força atômica no modo de monitoramento de gradientes de campo elétrico, denominado microscopia de força elétrica, para revelar as barreiras de potencial nos contornos de grão. Estas barreiras elétricas são associadas com o abrupto aumento na resistividade elétrica que ocorre a partir da temperatura de transição ferroelétrica- paraelétrica em BaTiO3 dopado com pequenas quantidades de doadores. Mostramos que para a composição utilizada neste estudo a largura das barreiras elétricas é da ordem de 350 nm-400 nm, presentes nos contornos de grãos de tamanho médio de 1µm.

Barium titanate (BaTiO3) based ceramics doped with La as donor (0.4at%t) and Mn as acceptor (150 ppm) were investigated through atomic force microscopy operating in electric force microscopy mode in order to reveal the potential barriers at grain boundaries. These barriers are associated with the steep rise in the resistivity above the ferroelectric-paraelectric phase transition temperature in BaTiO3 doped with small amounts of donor impurities. We show here that for such a composition the potential barrier width are of the order of 350-400 nm, present at grain boundaries of grains with size around 1 µm.

We have measured the collisional loss rate for cold strontium atoms held in a magneto-optical trap as a function of light intensity in the regime of low intensity (2-6 mW/cm²). The results confirm our recently proposed model, where we showed that the sudden increase of loss rate at low intensities does not depend on hyperfine structure changing collision only. The model, which is based on radiative escape mechanism and a light intensity dependent escape velocity, is able to reproduce quite well the behavior of the experimental observations. The data here reported may be of importance for a recent proposed application for cold trapped 88Sr atoms, as well as other trappable alkaline earth metal atoms such as Ca.