Grain-size effects on thermal properties of BaTiO3 ceramics

Abstract

Dense nanocrystalline BaTiO 3 ceramics are successfully prepared by the high pressure assisted sintering. Microstructures are observed by scanning electronic microscopes. The grain sizes are estimated to be about 30 and 150 nm. In comparison, BaTiO 3 ceramics with the grain size of 600 nm and 1.5 µm are fabricated by conventional pressure-less sintering. The thermal properties of BaTiO 3 ceramics with different grain sizes are investigated by differential scanning calorimetry and thermal expansion. The results suggest that the enthalpy values for the tetragonal-cubic transition decreased and the thermal expansion values increased with decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size.

Effect of Size on the Structural Transition and Magnetic Properties of Nano-CuFe2O4

“…As revealed in Figure , the size of nano-CuFe 2 O 4 can have a remarkable influence on the enthalpy of structural transition: the enthalpy of phase transformation decreases by about 3.5 times when the particle size is decreased by 2.5 times, which is in accord with those reported in the literature; ,, and there is a linear correlation between the enthalpy of structural transition and the reciprocal of size of nanoparticles, which are in good agreement with the above experimental results. The intersection point between the linear correlation equation and the Y -axis is the enthalpy of structural transition for bulk CuFe 2 O 4 , with a value of 1070.5 J·mol –1 .…”

“…Therefore, the correlation between the temperature of structural transition and the size of solid nanoparticles is opposite that of the porous nanoparticles. As revealed in Figure 5, the size of nano-CuFe 2 O 4 can have a remarkable influence on the enthalpy of structural transition: the enthalpy of phase transformation decreases by about 3.5 times when the particle size is decreased by 2.5 times, which is in accord with those reported in the literature; 15,27,29 As shown in Figure 6, with the size of nanoparticles decreasing, the entropy of structural transition decreases, which is consistent with the experimental results and theoretical calculation of size dependence of the structural transition entropy reported in the literature, 16 and the entropy of structural transition varies linearly with the reciprocal of size of nanoparticles.…”

“…Tveryanovich et al 14 obtained the nano-AgI with the thickness of the layers ranging from 10 to 100 nm using laser ablation and studied the structural transition of β to α with a Rigaku Ultima IV X-ray diffractometer, and they found that, with the decreasing size of nanoparticles, the temperature of the corresponding structural transition decreases. Xiao et al 15 performed a DSC test to investigate the structural transition of BaTiO 3 of different grain sizes, and the test results show that the structural transition enthalpy reduced with decreasing grain size. Jiang et al 16 proposed an improved phenomenological theory by taking the size effects on phenomenological coefficients into account.…”

Suppressed grain growth in highly porous barium titanate foams by two‐step sintering

“…Many of the relevant properties for these applications are affected by the microstructure, and more specifically the grain size of the material. Piezoelectric, dielectric, ferroelectric, thermal, and mechanical properties of barium titanate are all shown to be affected by grain size . More specifically, for the proposed use of foamed barium titanate for regenerative bone matrices where cell attachment, migration, and sprawl is of importance, it is very likely that the grain size and grain‐boundary concentration, which will change the morphology and surface energies of the struts, will play a major role.…”

“…Piezoelectric, dielectric, ferroelectric, thermal, and mechanical properties of barium titanate are all shown to be affected by grain size. [7][8][9][10][11] More specifically, for the proposed use of foamed barium titanate for regenerative bone matrices where cell attachment, migration, and sprawl is of importance, it is very likely that the grain size and grainboundary concentration, which will change the morphology and surface energies of the struts, will play a major role. A variety of techniques have been proposed for processing and fabrication of porous ceramics.…”