Ferroelectric BaTiO3 phase of orthorhombic crystal structure contained in nanoparticles

Ferroelectric BaTiO3 phase of a Pnma orthorhombic crystal structure is synthesized from a chemical method using a polymer complex of Ba2+ and Ti4+ with polyvinyl alcohol (PVA). After burning out the polymer at temperature as high as 550 °C in air for 2 h results in an average 15 nm crystallite BaTiO3 size, with lattice parameters a=0.6435 nm, b=0.5306 nm, c=0.8854 nm, and density 5.124 g∕cm3. The relationship between dielectric constant εr and temperature showed a single Curie transition temperature TC=131 °C, with as large a εr value as 263 at TC. A low value of dissipation factor tan δ, as small as 0.033 at room temperature (frequency f=1 kHz), with good insulating properties made the sample promising for use in uncooled infrared detectors and thermal imaging applications. The εr value is nearly independent of f value up to 100 kHz. A spectrum of sharp EPR signals of g values 2.21 to 1.88 characterizes three major kinds of VBa−, VTi3−, and Ti3+−Vo2+ paramagnetic species present in the imperfections.