Electric characterization by impedance spectroscopy of ceramics of niobate oxide of tetragonal tungsten bronze family with KSr2FeNb4O15 stoichiometry

• Grant number: 07/07421-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): December 01, 2007
• Effective date (End): November 30, 2009
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Nonmetallic Materials
• Principal Investigator: Silvania Lanfredi
• Grantee: Robson Lopes Grosso
• Host Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil

Abstract

This research project approach the electric characterization in ceramic samples of potassium strontium niobate doped with iron with KSr2FeNb4O15 stoichiometry, an oxide of the tetragonal tungsten bronze family (TTB). Ceramic materials with tetragonal tungsten bronze structure present, in general, high dielectric constants, ferroelectric and piezoelectric properties of scientific and technologic interest. Lead free ferroelectric materials termed of Tetragonal Tungsten Bronze (TTB) family exhibit potential application in technologic areas as linear dielectrics. KSr2FeNb4O15 phase will be prepared by mechanic mixture of oxide/carbonate using high efficiency milling process, an operational processing technique of Laboratory of Composites and Functional Ceramics (LaCCeF - FAPESP), DFQB/FCT/ UNESP. Pellets of KSr2FeNb4O15 powders will be uniaxialy pressed and sintered (in a box furnace) at several time, temperature and atmospheres sintering for the obtaining of dense ceramics. The electric characterization of the ceramic will be carried out by impedance spectroscopy in the frequency range from 5Hz to 13 MHz, between 25 oC and 700 oC. Based on a.c. measurements will be investigated the conductivity and dispersion dielectric phenomenon (tan x temperature and tan x frequency), at low frequency in several thermal cycles of measures (heating - cooling). This procedure permits identify the hysteresis in the system and to correlate with phase transitions. A furnace attached to the measure cellule will permit to performer the electric measurements since room temperature up to 700 oC. (AU)