Effect of oxygen vacancies on dielectric property and reliability of anti-ferroelectric PLZT applicable to EV-MLCC

A study on anti-ferroelectric (PbLa)(ZrTi)O₃ (PLZT) for electric vehicles (EV) applicable to DC-link was conducted. Multilayer ceramic capacitors (MLCCs) for DC-link require high-electric field properties and reliability. Oxygen vacancies are a major cause affecting insulation properties and reliability. There are acceptors and donors as methods for controlling the mobility and concentration of oxygen vacancies. The mobility and concentration of oxygen vacancies were simultaneously controlled, rather than individually controlled. Mn⁴⁺ was selected as the acceptor and Dy³⁺ was selected as the donor. After fixing Mn⁴⁺ = 5.0 mol% to (Pb_0.82La_0.12)(Zr_0.86Ti_0.14)O₃, insulation properties and reliability were evaluated according to Dy³⁺ = 5.0, 10.0, 15.0 and 20.0 mol%. A high sintered density was obtained at a temperature of 1200°C in a reduction atmosphere. When Mn⁴⁺ = 5.0 mol% and Dy³⁺ = 10.0 mol% were co-substituted into PLZT, a dielectric constant of about 1800 and a breakdown voltage of about 12 kV mm⁻¹ were obtained. In the co-substituted PLZT, capacitance change and insulation degradation properties were greatly improved. Oxygen vacancy mobility and concentration control were effective in reliability properties. Thermally stimulated depolarization current (TSDC) was analysed to confirm the polarization of oxygen vacancies. TSDC increased with electric field and time. TSDC decreased in co-substituted PLZT compared to un-substituted PLZT. A factor affecting TSDC is the behaviour of oxygen vacancies. Based on the result, the oxygen vacancies are polarized and moved by the application of an electric field, resulting in degradation of insulating properties.