Effects of Different Element Doping on Microstructure and Thermoelectric Properties of CaTiO3

doi:10.15541/jim20230288

Abstract

Abstract:

Despite the growing research in CaTiO₃ as a novel high-temperature oxide thermoelectric material, effects of various elements doping on the microstructure and thermoelectric performance of CaTiO₃ have not been fully understood. Here, a combination of hydrothermal synthesis and vacuum hot-press sintering techniques was employed to fabricate polycrystalline bulks of CaTiO₃ doped with six elements: Cr, Nb, Eu, Dy, Ce, and La. Cr doping resulted in substantial precipitation of nanoscale Cr phases, leading to a severely compromised power factor and a ZT of only 0.012 at 983 K due to insufficient donor element concentration in the matrix. Incorporating Eu as a donor carrier in the matrix is proved ineffective, resulting in a marginal ZT enhancement of 0.141 at 1031 K. Nb doping resulted in the formation of micrometer-scale Nb phases with high thermal conductivity, leading to an elevation in thermal conductivity. However, the relatively higher Nb concentration in the matrix provided carriers, resulting in a noticeable ZT improvement to 0.263 at 1013 K. On the contrary, Dy, Ce, and La doping exhibited remarkable dual functionality as donor dopants and point defects, thereby significantly enhancing the power factor and concurrently reducing the lattice thermal conductivity. These improvements were achieved through efficient manipulation of carrier concentration and implementation of phonon scattering. As a result, the thermoelectric figure of merit (ZT) reached 0.357, 0.398, and 0.329 at 1031 K for Dy, Ce, and La-doped CaTiO₃ bulks, respectively. These values represent an extraordinary improvement of 296%, 342%, and 265%, respectively, as compared to that of the pristine CaTiO₃ (0.096 @1031 K). Notably, Dy-doped samples exhibited significantly reduced lattice thermal conductivity and comparatively higher power factors over the entire temperature range. Regulating Dy content and enhancing the second phase at grain boundaries enabled the decoupling of electrical and thermal transport properties, potentially surpassing the current ZT record of CaTiO₃. This study provides valuable insights into the relationships among composition, structure, and performance in CaTiO₃ doped with various elements, offering theoretical support for high-temperature thermoelectric applications.

Key words: CaTiO₃, oxide thermoelectric material, microstructure, element doping

CLC Number:

TQ174

LI Jianbo, TIAN Zhen, JIANG Quanwei, YU Lifeng, KANG Huijun, CAO Zhiqiang, WANG Tongmin. Effects of Different Element Doping on Microstructure and Thermoelectric Properties of CaTiO₃[J]. Journal of Inorganic Materials, 2023, 38(12): 1396-1404.

Figures/Tables 13

Fig. 1 Schematic diagram of crystal structure for CaTiO3 at room temperature

Fig. 2 Schematic diagram of synthesis of CaTiO3 by hydrothermal method

Fig. 3 XRD patterns of CaTiO3 (a, b) powders and (c, d) bulks doped with different elements; (e) SEM image of powder and (f) BES image of bulk for the pristine CaTiO3 sample

Table 1 Atomic radii and ionic radii of different atoms

Atom	Atomic radius/pm	Ionic radius/pm
Ca	174	99 (M²⁺)
Ti	132	68 (M⁴⁺)
Cr	118	84 (M³⁺)
Nb	134	70 (M⁵⁺)
Dy	177.3	90.8 (M³⁺)
Ce	182.4	103.4 (M³⁺)
La	187.7	106 (M³⁺)

Fig. 4 SEM images, element mappings, and corresponding EDS spectra of (a) Cr20, (b) Nb20, (c) Eu20, (d) Dy20, (e) Ce20, and (f) La20 powders

Fig. 5 EPMA images, element mappings, and corresponding chemical compositions of (a) Cr20, (b) Nb20, (c) Eu20, (d) Dy20, (e) Ce20, and (f) La20 bulks Unit in tables: % (in atom)

Fig. 6 Temperature-dependence of (a) electrical conductivity, (b) Seebeck coefficient with inset showing enlarged plots in temperature range of 300-600 K, (d) power factor, (f) total thermal conductivity, (g) lattice thermal conductivity, and (h) ZT of Cr20, Nb20, Eu20, Dy20, Ce20, and La20 bulks, and their (c) carrier concentration at 320 K, (e) Pisarenko curves and (i) ZT compared to literature[18⇓⇓-21]

Table S1 Summary of the raw materials used for experiments

Chemical composition	Purity	Production factories
CaCl₂	≥ 99.99%	Aladdin
DyCl₃·6H₂O	≥ 99.99%	Aladdin
EuCl₃·6H₂O	≥ 99.99%	Aladdin
La(NO₃)₃·6H₂O	≥ 99.99%	Aladdin
CeCl₃·7H₂O	≥ 99.99%	Aladdin
CrCl₃	≥ 99.99%	Aladdin
NbCl₅	≥ 99.9%	Aladdin
C₁₆H₃₆O₄Ti	≥ 99%	Aladdin
NbCl₅	≥ 99.9%	Aladdin
NaOH	≥ 99%	Aladdin
C₂H₆O₂	≥ 95%	Aladdin

Fig. S1 XRD pattern of the CaTi0.8Cr0.2O3 bulk

Fig. S2 Temperature-dependent (a) thermal diffusion, (b) specific heat, (c) electrical thermal conductivity, and (d) Lorenz constant for pristine for Pristine CaTiO3, Cr20, Nb20, Eu20, Dy20, Ce20, and La20 samples

Fig. S3 EPMA backscattering images of the CaTi0.8Nb0.2O3 (Nb20) bulk sintered at (a) 1400, (b) 1450, and (c) 1500 ℃, respectively

Fig. S4 Temperature-dependence of the (a) electrical conductivity, (b) Seebeck coefficient, and (c) power factor of CaTi0.8Nb0.2O3 (Nb20) sintered at (a) 1400, (b) 1450, and (c) 1500 ℃, respectively

Table S2 Nominal chemical compositions, sample codes, measured densities, theoretical densities, and relative densities of the prepared bulk samples

Nominal chemical composition	Composition sample code	Measured density/ (g·cm^-3)	Theoretical density/(g·cm^-3)	Relative density/%
CaTiO₃	Pristine	3.85	4.04	95.2
CaTi_0.8Cr_0.2O₃	Cr20	3.89	4.06	95.8
CaTi_0.8Nb_0.2O₃	Nb20	4.07	4.30	94.6
Eu_0.2Ca_0.8TiO₃	Eu20	4.39	4.70	93.4
Dy_0.2Ca_0.8TiO₃	Dy20	4.48	4.76	94.1
Ce_0.2Ca_0.8TiO₃	Ce20	4.40	4.63	95.0
La_0.2Ca_0.8TiO₃	La20	4.19	4.62	90.7

References 36

[1]	BRENDAN J K, CHRISTOPHER J H, BRYAN C C. Phase transitions in perovskite at elevated temperatures: a powder neutron diffraction study. Journal of Physics: Condensed Matter, 1999, 11(6): 1479. DOI URL
[2]	SHI J, GUO L. ABO₃-based photocatalysts for water splitting. Progress in Natural Science: Materials International, 2012, 22(6): 592. DOI URL
[3]	MANAN A, NAWAZ A, AHMAD A S, et al. Preparation and microwave dielectric properties of CaTiO₃added Mg_0.95Ni_0.05-Ti_0.98Zr_0.02O₃ composite ceramics for high frequency applications. Materials Science-Poland, 37(4): 639. DOI URL
[4]	OLIVEIRA R, SILVA R, DE MORAIS J, et al. Effects of CaTiO₃ addition on the microwave dielectric properties and antenna properties of BiVO₄ ceramics. Composites Part B: Engineering, 2019, 175: 107122.
[5]	SAHOO S, DASH U, PARASHAR S, et al. Frequency and temperature dependent electrical characteristics of CaTiO₃nano-ceramic prepared by high-energy ball milling. Journal of Advanced Ceramics, 2013, 2: 291.
[6]	CAI J, CAO A, HUANG J, et al. Understanding oxygen vacancies in disorder-engineered surface and subsurface of CaTiO3 nanosheets on photocatalytic hydrogen evolution. Applied Catalysis B: Environmental, 2020, 267: 118378. DOI URL
[7]	MANJUNATH K, G THIMMANNA C. Studies on synthesis, characterization and applications of nano CaTiO₃powder. Current Nanomaterials, 2016, 1(2): 145. DOI URL
[8]	PASSI M, PAL B. A review on CaTiO₃ photocatalyst: activity enhancement methods and photocatalytic applications. Powder Technology, 2021, 388: 274.
[9]	SINGH B K, HAFEEZ M A, KIM H, et al. Inorganic waste forms for efficient immobilization of radionuclides. ACS ES&T Engineering, 2021, 1(8): 1149.
[10]	CHEN Y, LIN Z, ZHANG Z, et al. Dielectric and MLCC property of modified (Sr,Ca)TiO₃based energy storage ceramic. Journal of Inorganic Materials, 2022, 37(9): 976. DOI URL
[11]	ZHOU W M, CHEN Q H, KE M Z, et al. Preparation and properties of CaTiO₃:Pr³⁺/TiO₂-mica fluorescent pearlescent pigments. Journal of Inorganic Materials, 2014, 29(12): 1275. DOI URL
[12]	TIAN B Z, JIANG X P, CHEN J, et al. Low lattice thermal conductivity and enhanced thermoelectric performance of SnTe via chemical electroless plating of Ag. Rare Metals, 2022, 41(1): 86. DOI
[13]	LIU K J, ZHANG Z W, CHEN C, et al. Entropy engineering in CaZn₂Sb₂-YbMg₂Sb₂ Zintl alloys for enhanced thermoelectric performance. Rare Metals, 2022, 41(9): 2998. DOI
[14]	ZHANG R Z, HU X Y, GUO P, et al. Thermoelectric transport coefficients of n-doped CaTiO₃, SrTiO₃ and BaTiO₃: a theoretical study. Physica B: Condensed Matter, 2012, 407(7): 1114. DOI URL
[15]	NOOR N A, ALAY-E-ABBAS S M, HASSAN M, et al. The under-pressure behaviour of mechanical, electronic and optical properties of calcium titanate and its ground state thermoelectric response. Philosophical Magazine, 2017, 97(22): 1884. DOI URL
[16]	ZHOU H Y, LIU X Q, ZHU X L, et al. CaTiO₃ linear dielectric ceramics with greatly enhanced dielectric strength and energy storage density. Journal of the American Ceramic Society, 2018, 101(5): 1999. DOI URL
[17]	CAVALCANTE L S, MARQUES V S, SCZANCOSKI J C, et al. Synthesis, structural refinement and optical behavior of CaTiO₃ powders: a comparative study of processing in different furnaces. Chemical Engineering Journal, 2008, 143(1): 299. DOI URL
[18]	LI J, WANG Y, YANG X, et al. Processing bulk insulating CaTiO₃ into a high-performance thermoelectric material. Chemical Engineering Journal, 2022, 428: 131121.
[19]	XIAO X, WIDENMEYER M, MUELLER K, et al. A squeeze on the perovskite structure improves the thermoelectric performance of europium calcium titanates. Materials Today Physics, 2018, 7: 96.
[20]	XIAO X, XIE W, WIDENMEYER M, et al. Synergistic effects of Eu and Nb dual substitution on improving the thermoelectric performance of the natural perovskite CaTiO₃. Materials Today Physics, 2022, 26: 100741.
[21]	LI J, WANG Y, JIANG X, et al. Emerging homogeneous superlattices in CaTiO₃bulk thermoelectric materials. Materials Horizons, 2023, 10(2): 454. DOI URL
[22]	CHI F, QIN Y, ZHOU S, et al. Eu³⁺-site occupation in CaTiO₃ perovskite material at low temperature. Current Applied Physics, 2017, 17(1): 24. DOI URL
[23]	ITO M, MATSUDA T. Thermoelectric properties of non-doped and Y-doped SrTiO₃ polycrystals synthesized by polymerized complex process and hot pressing. Journal of Alloys and Compounds, 2009, 477(1): 473. DOI URL
[24]	WANG Y, FAN H J. Sr_1-_xLa_xTiO₃ nanoparticles: synthesis, characterization and enhanced thermoelectric response. Scripta Materialia, 2011, 65(3): 190. DOI URL
[25]	SHANG P P, ZHANG B P, LI J F, et al. Effect of sintering temperature on thermoelectric properties of La-doped SrTiO₃ceramics prepared by Sol-Gel process and spark plasma sintering. Solid State Sciences, 2010, 12(8): 1341. DOI URL
[26]	KIKUCHI A, OKINAKA N, AKIYAMA T. A large thermoelectric figure of merit of La-doped SrTiO₃ prepared by combustion synthesis with post-spark plasma sintering. Scripta Materialia, 2010, 63(4): 407. DOI URL
[27]	LI J B, WANG J, LI J F, et al. Broadening the temperature range for high thermoelectric performance of bulk polycrystalline strontium titanate by controlling the electronic transport properties. Journal of Materials Chemistry C, 2018, 6(28): 7594. DOI URL
[28]	WANG J, ZHANG B Y, KANG H J, et al. Record high thermoelectric performance in bulk SrTiO₃ via nano-scale modulation doping. Nano Energy, 2017, 35: 387.
[29]	LU Z, ZHANG H, LEI W, et al. High-figure-of-merit thermoelectric La-doped A-site-deficient SrTiO₃ ceramics. Chemistry of Materials, 2016, 28(3): 925. DOI URL
[30]	KIMIJIMA T, KANIE K, NAKAYA M, et al. Hydrothermal synthesis of size- and shape-controlled CaTiO₃ fine particles and their photocatalytic activity. CrystEngComm, 2014, 16(25): 5591. DOI URL
[31]	FU B G, YANG J C, GAO Z K, et al. Hot pressing sintering process and sintering mechanism of W-La₂O₃-Y₂O₃-ZrO₂. Rare Metals, 2021, 40(7): 1949. DOI
[32]	KIM Y J, ZHAO L D, KANATZIDIS M G, et al. Analysis of nanoprecipitates in a Na-doped PbTe-SrTe thermoelectric material with a high figure of merit. ACS Applied Materials & Interfaces, 2017, 9(26): 21791.
[33]	MOOS R, GNUDI A, HÄRDTL K H. Thermopower of Sr_1-_xLa_xTiO₃ ceramics. Journal of Applied Physics, 1995, 78(8): 5042. DOI URL
[34]	KIM H S, GIBBS Z M, TANG Y, et al. Characterization of Lorenz number with Seebeck coefficient measurement. APL Materials, 2015, 3(4): 041506. DOI URL
[35]	SINGARAVELU S, KLOPF J, KRAFFT G, et al. Laser nitriding of niobium for application to superconducting radio-frequency accelerator cavities. Journal of Vacuum Science & Technology B, 2011, 29(6): 061803.
[36]	COOK B A, KRAMER M J, HARRINGA J L, et al. Analysis of nanostructuring in high figure-of-merit Ag_1-_xPb_mSbTe₂₊_m thermoelectric materials. Advanced Functional Materials, 2009, 19(8): 1254. DOI URL

Effects of Different Element Doping on Microstructure and Thermoelectric Properties of CaTiO₃

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