Controllable negative thermal expansion, ferroelectric and semiconducting properties in PbTiO3–Bi(Co2/3Nb1/3)O3 solid solutions

Abstract

Semiconductor functional materials have been widely applied in electronic devices. However, the reliability and lifetime of the devices suffer from the undesirable mismatch of the coefficients of thermal expansion. It is important to develop semiconductor materials with controllable thermal expansion. Here, we develop a remarkable group of ferroelectric semiconductor materials (1 − x)PbTiO₃–xBi(Co_2/3Nb_1/3)O₃ (PT–100xBCN) that have not only tunable electronic and optical properties, but also controllable negative, zero, and positive thermal expansion. Through the BCN chemical substitution, the bandgap (E_g) is reduced from 2.60 eV to 2.26 eV to achieve semiconducting properties in PbTiO₃-based ferroelectrics. Meanwhile, we have achieved a gradual transition from negative, to zero, and then to positive thermal expansion (α_V: −12.3 × 10⁻⁶ to 7.4 × 10⁻⁶ K⁻¹). Besides, PT–BCN exhibits ferroelectric and piezoelectric properties. The relatively high piezoelectric coefficient d₃₃ ∼ 200 pC N⁻¹ was achieved in the composition of PT–42BCN near the morphotropic phase boundary. PT–BCN shows good negative temperature coefficient (NTC) thermistor characteristics. The coexistence of light absorption, thermal expansion, and electronic properties in PT–BCN makes it a promising material for future applications. The present study would offer an approach to developing and exploring new multifunctional semiconducting materials with controllable thermal expansion.