High thermoelectric performance of Nb-doped SrTiO₃ bulk materials with different doping levels

Abstract

Nb-doped SrTiO3 bulk materials with high quality are fabricated using a facile process.

Phonon-glass electron-crystal behaviour by A site disorder in n-type thermoelectric oxides

“…S9, ESI †) are comparable to many of the titanates reported previously, which were doped on either the A or B sites. 27,28,36,37 The observation of high S and σ suggests that the unique band structure of STO, consisting of heavy and light electrons, that allows for high power factors is retained in La0.5Na0.5Ti1-xNbxO3 despite the slight distortion of the structure away from cubic symmetry, consistent with the DFT calculations. A maximum power factor of 0.620.07 mW m -1 K -2 was obtained for La0.5Na0.5Ti0.8Nb0.2O3 at ≈700 K (Fig.…”

A and B site doping of a phonon-glass perovskite oxide thermoelectric

“…One of the more useful features resulting from the complete replacement of Sr 2+ for a charge balanced mixture of La 3+ and K + in La 0.5 K 0.5 TiO 3 is that the chemical and structural exibility of the perovskite structure is maintained. Electron doping in SrTiO 3 involves the incorporation of an aliovalent cation with higher charge, such as Ln 3+ on the A site or Nb 5+ on the B site, 42,45,46 which through charge compensation mechanisms reduces a sufficient amount of Ti 4+ to Ti 3+ giving rise to electronic transport. Even though the A site in La 0.5 K 0.5 TiO 3 has a disordered cation arrangement, the exible structural chemistry enables the introduction of electronic carriers through doping of either the A or B site.…”

“…The observed temperature dependencies of both s and S for all compositions are similar to many doped titanate thermoelectrics reported in the literature. 40,42,46,47 Maxima in s are observed between 500-600 K and are associated with increased resistance from acceptor-based phases which are localised to the grain boundaries. 48 The negative values of S indicate electron doping of predominantly n-type carriers within all compositions, and both A and B site doped materials exhibit decreasing |S| with increasing carrier concentration which is expected for metals or parabolic band semiconductors through eqn (8)…”

Effects of Pr and Yb Dual Doping on the Thermoelectric Properties of CaMnO3

“…The substitution of the divalent Ca 2+ cation by trivalent Pr and Yb ions induces the formation of Mn 3+ with an eg1 configuration as an electron carrier, resulting in a lower absolute Seebeck coefficient. The absolute Seebeck coefficient can be calculated by the following model proposed for degenerate semiconductors [41]:$\mathrm{S}=\frac{8{\pi }^2{k}_B^2}{3e{h}^2}m·\mathrm{T} {\left(\frac{\pi }{3n}\right)}^{\frac{2}{3}}$ where k B is the Boltzmann constant and n and m * refer to the carrier concentration and the effective mass of the carrier, respectively. The absolute Seebeck coefficient values are inversely proportional to n .…”