Investigation of PTCR effect and microdefects in Nb2O5-doped BaTiO3-based ceramics by positron annihilation techniques

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The influence of Nb2O5-doped concentration on the positive temperature coefficient of resistance (PTCR) effect, electrical properties and microdefects of (Ba[Formula: see text]Sr[Formula: see text])(TiNb[Formula: see text])O3 (BSTN) ceramics were investigated. Firing was conducted at 1350[Formula: see text]C for 2 h in air. The donor-doped content affected the electrical properties, PTCR effect and formation of the microdefect type of the BSTN samples. The room temperature resistivity of the BSTN specimens first decreased and then increased with increasing donor-doped content in the range of 0.2 mol.% Nb[Formula: see text] to 0.5 mol.% Nb[Formula: see text]. Moreover, the information on microdefects in BSTN ceramics was demonstrated by coincidence Doppler broadening spectrum. The influence of the defects on the PTCR characteristics of the ceramics was also revealed.