Influence of nanometric microstructural development on thermophysical properties of lanthanum-doped strontium titanate

• Published in: Materials chemistry and physics Vol. 270; p. 124867
• Main Authors: Ibrahim, Idza Riati, Matori, Khamirul Amin, Ismail, Ismayadi, Rusly, Siti Nor Ain, Nazlan, Rodziah, Yusof, Nor Hidayat, Mohd Zaid, Mohd Hafiz, Chanlek, Narong, Nakajima, Hideki, Mat Daud, Norni Hidayawati, Bahmanrokh, Ghazaleh
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-09-2021; Elsevier BV
• Subjects: Ball milling; Crystal defects; Crystal structure; Diffusivity; Doping; Grain boundaries; Grain growth; Grain size; Lanthanum; Lanthanum-doped strontium titanate; Microstructural; Morphological; Morphology; Phonons; Scattering; Sintering; Strontium; Strontium titanates; Thermal diffusivity; Thermoelectric materials; Thermophysical properties; Thermal diffusivity; Lanthanum-doped strontium titanate; Morphological; Microstructural
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2021.124867

The evolution of imperfect crystal from a highly amorphous structure to an ordered crystalline structure via sintering has demonstrated a significant development onto the thermophysical properties. Therefore, a series of La-doped strontium titanate with different morphological properties have been synthesized via high energy ball milling with subsequent sintering. Doping of lanthanum tends to inhibit the grain growth where a significant reduction of grain size (range from 34 nm to 0.47 μm) could be observed. A large amount of grain boundaries presence with fine grains, resulting from lanthanum doping, has enhanced phonon scattering, thus yielding a low heat propagation in La-doped SrTiO3. Besides acting as a grain growth inhibitor, lanthanum also acts as a scattering centre due to imperfection created by the doping. The scattering mechanisms significantly decrease the phonon mean free path. Consequently, the thermal diffusivity has been efficiently reduced to 1.1 mm2/s as compared to that of pure SrTiO3 which showed a value of about 3.8 mm2/s, both observed for the complete phase polycrystalline materials. The systematic development of thermophysical and morphological properties of La-doped SrTiO3 can be served as a preliminary guide to engineer thermoelectric materials with low thermal diffusivity.
•Grain growth was inhibited by lanthanum doping, thus resulting the nanometric grains.•Nanometric grains limit the heat transfer due to the imperfection crystals.•Thermal diffusivity of lanthanum doped was efficiently reduced as compared to pure SrTiO3.