Glass-like phase transitions and dielectric nonlinearity in lead magnesium niobate crystals

Abstract

Temperature dependence of differential dielectric nonlinearities β = ∂²ϵ/∂ E² of lead-magnesium-niobate crystals (PMN) has been studied using small-signal dielectric permittivity ϵ data when a bias electric field E₌ is applied to the crystal. The nonergodicity of PMN is observed at temperatures 150-300 K. As a bias electric field E₌ is decreased (50 ≤ E₌ < 500 V/cm), the value β is increased. At fields 500 ≤ E₌ < 1,000 V/cm β practically does not depend on E₌. Two minima observed in temperature dependence β correspond to phase transitions into glass-like state in PMN.

Key Words:

• Lead Magnesium-Niobate
• glass-like state
• diffused phase transitions
• differential dielectric nonlinearity