Experimental Evaluation of the Acceptor‐States Compensation in Positive‐Temperature‐Coefficient‐Type Barium Titanate

Abstract

Experimental evidence shows that the acceptor-state levels in Sb-doped positive-temperature-coefficient-type BaTi03 are compensated up to a critical acceptor-state density. Using the slope of the natural logarithm of the resistivity with re-' spect to 1/T instead of maximum resistivity as a measure for the acceptor-state density, it is possible to estimate this critical value. The value obtained (4.2 X 10" m-') is believed to be the first reported estimate based on experimental data. It is in good agreement with the estimate of 6 X 10" m-' (first reported by Jonker) obtained from the spontaneous polarization of BaTi03. This shows that the ferroelectric behavior of BaTi03 is indeed a feasible explanation for the low resistivity below the Curie point, as proposed by Jonker.[Key words: positive temperature coefficient of resistivity, barium titanate, acceptor, polarization, ferroelectrics.]

Influence of Reoxidation on Silica-Containing Barium Titanate Ceramics for PTCR Thermistors Prepared by Tape Casting

“…Furthermore, the foregoing explanation of ferroelectricity rebuilding mechanism can be supported by the interpretation of Huybrechts et al [11], which focuses on the relationship between the RT resistivity and N S . The proposition demonstrates that the RT resistivity depends very strongly upon the N S , if no ferroelectrical compensation occurs at grain boundaries.…”

“…C and θ represent the Curie constant (C = 1.5 × 10 5 K) and the extrapolated Curie-Weiss temperature (θ = 383 K) [11]. Figure 5 plots the temperature-dependent resistivity The inset of Figure 5 shows the influence of reoxidation temperature on the N S values, which are within the range of 2.1 -2.5 × 10 13 cm -2 .…”

“…Thus, the donor density (N d ) can be calculated to be 4.57 × 10 17 cm -3 , from the corresponding RT resistivity (ρ RT ) of the reduced sample by N d = 1/ρ RT qμ. Here, μ is the electron mobility in BaTiO 3 and was estimated to be 0.5 cm 2 •V -1 ·s -1 [11]. The estimate of acceptor-state density (N S ) is completed by using Hybrechts's method [11], which is based on the linear relationship between lnρ and T -1 of the BaTiO 3 ceramics.…”

“…Here, μ is the electron mobility in BaTiO 3 and was estimated to be 0.5 cm 2 •V -1 ·s -1 [11]. The estimate of acceptor-state density (N S ) is completed by using Hybrechts's method [11], which is based on the linear relationship between lnρ and T -1 of the BaTiO 3 ceramics. If S is the slope of the linear function, N S can be estimated according to Equation 1, …”

Reoxidation Effects of Ba‐Excessive Barium Titanate Ceramics for Laminated Positive Temperature Coefficient Thermistors

“…It is noted that for present ceramic specimens, the estimated values of N S f( p ) locate in the region of 2 × 10 12 –6 × 10 12 cm −2 , quite lower than the results in other reports . There would be two main possible reasons.…”