Curie Temperature (T_C)

The temperature at which a ferroelectric material undergoes a transition from the ferroelectric to the paraelectric phase. Above T_C, spontaneous polarization disappears.

Burns Temperature (T_B)

The temperature above which the material behaves as a normal paraelectric. Below T_B, local regions of spontaneous polarization (PNRs) begin to form.

Freezing Temperature (T_f)

The temperature below which the motion of Polar Nano Regions (PNRs) becomes frozen, resulting in a transition to a non-ergodic relaxor state with remanent polarization.

Temperature of Dielectric Maximum (T_m)

The temperature at which dielectric permittivity reaches its maximum value. In relaxors, T_m is broad and frequency-dependent, unlike the sharp T_C of normal ferroelectrics.

Polar Nano Regions (PNRs)

Nanoscale clusters (10–50 nm) of locally aligned dipoles forming below the Burns temperature. Their dynamic behavior governs the dielectric response of relaxor ferroelectrics.

Ergodic State

A high-temperature, dynamic state where PNRs fluctuate freely and reversibly, showing frequency-dependent polarization behavior.

Non-Ergodic State

A low-temperature, frozen state where PNRs become static, leading to hysteresis and remanent polarization similar to classical ferroelectrics.

Diffuse Phase Transition (DPT)

A gradual dielectric transition characterized by a broad permittivity peak, typical of relaxor ferroelectrics with compositional disorder.

Piezoelectric Effect

The generation of electric charge in response to mechanical stress, or vice versa. Prominent in non-centrosymmetric ferroelectric and relaxor materials.

Electrostriction

A quadratic coupling between electric polarization and mechanical strain, intrinsic to all dielectrics and significant in ferroelectric and relaxor systems.

Maxwell–Wagner Polarization

Interfacial polarization arising from charge accumulation at grain boundaries or interfaces, often observed in ceramics and composite relaxors.