Grain-size effects on dielectric and piezoelectric properties of poled BaTiO3 ceramics

Domain Wall Displacement is the Origin of Superior Permittivity and Piezoelectricity in BaTiO3 at Intermediate Grain Sizes

“…Within the investigated grain size range,  r is observed to be maximum (>5000) at ~2 µm and values of  r decrease both above and below this grain size, which agrees with previously reported trends [3,4,9,10,11]. The permittivity was also measured as a function of temperature up to temperatures exceeding the 6 Curie temperature (T c ) and the response at 1 kHz is reported in the supporting information. The T c remains nearly constant for all grain sizes and the associated loss increases slightly with decreasing grain size as expected.…”

“…The superior  r values of BaTiO 3 [7] and, furthermore, cannot be explained by orientational averaging of the single crystal anisotropic permittivity values. Limited studies have also shown comparable increases in the piezoelectric coefficients, d 33 or d 31 , at intermediate grain sizes near 1 µm [6,21].…”

“…In polycrystalline ferroelectrics, size effects are chiefly evident in materials properties such as the relative dielectric permittivity ( r ) and piezoelectric coefficients (e.g., d 33 and d 31 ). For polycrystalline barium titanate (BaTiO 3 ), the effect of grain size on the relative permittivity has been extensively reported over the past decades [3,4,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and is of particular relevance to the continuous size reduction of BaTiO 3 capacitors. Within the grain size range of 1-10 µm, it is now widely accepted that  r of polycrystalline BaTiO 3 increases with decreasing grain size, reaching a value of 5000, or higher, as the grain size approaches 1 µm.…”

Effect of grain size on domain structures, dielectric and thermal depoling of Nd-substituted bismuth titanate ceramics

“…24 for a succinct chronological review), but a clear understanding has not been achieved yet. 25,26 In this instance, the higher dielectric permittivity of BNT750 seems to be related to the higher internal mechanical stresses linked with single domain single grain structure as previously modeled. 27 The higher loss of BNT1000 can be attributed to the extrinsic contribution produced by the movement of the ferroelectric domain walls.…”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…[199][200][201][202] An optimal grain size is obtained when a maximized density of domains (and domain walls) leads to a proper balance between non-180° switchable domains and minimized back switching. [201][202][203][204] Excessive grain size leads to deterioration of dielectric and electromechanical properties due to disproportionate back switching. 202 On the other hand, too small grain size leads to suppression of ferroelectricity due to diminished non-cubic distortions.…”