Mn-Doped BaO–(Nd0.7,Sm0.3)2O3–4TiO2 Ceramic Sintered in a Reducing Atmosphere

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The effect of MnCO3 doping from 0 to 55 mol % into BaO–(Nd0.7Sm0.3)2O3–4TiO2 (BNST) sintered in a reducing atmosphere on the phase transformation, microstructure and electrical properties was studied. The variation of $d$-spacing with Mn content can be divided into three regimes in this study. In regime (I), 0 to 5 mol % Mn-doped BNST, the $d$-spacing decreases successively until 5 mol % which is the maximum solubility, because Mn+3 is incorporated into Ti+4-sites of BNST. In regime (II), 5 to 42 mol % Mn-doped BNST, the $d$-spacing remains constant and Mn2O3 is precipitated because the amount of MnCO3 doped is more than the solubility. In regime (III), 43 to 55 mol % Mn-doped BNST, the $d$-spacing is the same as BNST without MnCO3 doping. Heavily doping MnCO3 into BNST gives rise to two parallel reactions, forming two ternary systems, BaO–(Nd,Sm)2O3–TiO2 and BaO–(Nd,Sm)2O3–Mn2O3. Mn-doped BNST sintered in a reducing atmosphere is in a semiconducing state in regimes (I) and (II), because the concentration of free electron is higher than that of the acceptors. In contrast, Mn-doped BNST in regime (III) sintered in a reducing atmosphere is in an insulating state because the concentration of the acceptors is higher than that of liberated free electron.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2007-04-15