Low-frequency dielectric spectroscopy and electrical properties of Ca[B3O4(OH)3]·H2O single crystals near the phase transition

The dielectric properties and polarization of ferroelectric Ca[B3O4(OH)3]·H2O (colemanite) crystals are studied near the Curie temperature. The real part of dielectric permittivity (έ′), dielectric losses (tanδ), pyroelectric coefficient (γ), and thermally stimulated depolarization currents are measured from -50 to 50°C. To assess the detailed nature of the phase transition (Curie temperature tC~-7°C), the temperature dependences of έ′ and tan δ and are measured at frequencies f = 0.8-20 kHz. The results are used to determine σ′(ω) (where ω=πf ) and σ′(T) and evaluate the activation energy. The γ(t) data indicate that colemanite undergoes a diffuse phase transition.