Hydrothermal Synthesis of Nanometer‐Sized Barium Titanate Powders: Control of Barium/Titanium Ratio, Sintering, and Dielectric Properties

Abstract

Nanometer-sized BaTiO 3 powders have been synthesized hydrothermally from Ba(OH) 2 and titanium alkoxide at 150°C for 2 h, and the Ba/Ti ratio has been measured with an accuracy of ±0.003. Stoichiometric powders can be obtained by adjusting the Ba/Ti ratio of the reactants to a value of 1.018. At a lower Ba/Ti ratio, the solubility of Ba(OH) 2 prevents full incorporation of barium, and bariumdeficient powders result. A higher Ba/Ti ratio leads to the incorporation of excess barium in the powder. K s (BaTiO 3 ,-25°C) = 7 × 10 −8 has been calculated for the equilibrium reaction. From this result, two reproducible processes for the synthesis of stoichiometric BaTiO 3 are proposed. The processes rely only on very accurate control of the chemical composition (Ba/Ti ratio) of the precursor suspension. The sintering behavior of powders having Ba/Ti ratio values between 0.965 and 1.011 is described from results of dilatometric measurements and isothermal sintering. Roomtemperature dielectric constants as high as 5600 and losses as low as 0.009 have been obtained for a stoichiometry slightly less than 1.000. It is expected that optimum sintering behavior and electrical properties are obtained in the stoichiometry range 0.995-1.000.

Low‐Temperature Synthesis and Thermodynamic and Electrical Properties of Barium Titanate Nanorods

“…In Figure 8(b) one can note that for both ceramic samples the dielectric loss decreases with frequency increasing. Moreover, the values of this dielectric parameter are below 0.05, values comparable with the earlier reports of conventionally sintered barium titanate ceramics [46,47].…”

Dielectric properties of vanadium doped barium titanate synthesized via high-energy ball milling

“…Such properties of BaTiO 3 can be achieved through a modification of its crystal structure by a substitution of foreign metal * This paper was presented at XIX International Seminar on Physics and Chemistry of Solids (ISPCS) and Advanced Materials, Częstochowa, 12 -15 June, 2013. † E-mail: piotrdulian@indy.chemia.pk.edu.pl ions to produce a material with an appropriate Ba/Ti ratio and size of grains [5][6][7][8]. Despite the physicochemical investigations of this compound conducted for decades there is still no clear explanation for the origins of its ferroelectricity.…”

Generality of the environmentally benign catecholate method to the synthesis of barium-based perovskites

“…Barium titanate ceramics, when properly doped, are also semi-conductive and they exhibit an anomalous sharp jump of resistivity at the Curie temperature (6). The positive temperature coefficient of resistivity leads to the production of thermistors, level sensors, and self-regulating heaters (4,6). Barium titanate also has excellent ferroelectric properties which allow it to be used in the production of chip capacitors (7,8).…”

“…It is essentially used for multi-layered ceramic capacitors in computers, aerospace, and communication technologies (2Á5). Barium titanate ceramics, when properly doped, are also semi-conductive and they exhibit an anomalous sharp jump of resistivity at the Curie temperature (6). The positive temperature coefficient of resistivity leads to the production of thermistors, level sensors, and self-regulating heaters (4,6).…”

“…Previous production methods for these bariumbased oxides included hydrothermal method (1,3,6,7,12,13), solid-state (14Á18), high-gravity reactive precipitation (4,5), spray coprecipitation (8), polymerized complex reaction (19), low-temperature aqueous preparation (20), aqueous coprecipitation reaction (21), solÁgel (22), oxalate processing (10), hydrolysis (23), thermal decomposition (24), and the catecholate method (2). All of the synthetic pathways previously mentioned presented inferior stoichiometric control over the barium-to-X (X 0Ti, Zr, Hf) ratio compared to the catecholate method.…”