Effect of grain reffinement on properties of pore free strontium doped BaTiO3 dielectric ceramics

Abstract

In this study the effects of Sr addition and sintering p,lI<llneters em the microstructure and dielectric properties of BaT10) based CeramlCS were studicd. Ba,),)Sr01TiOJ, BlIi)sSro2TiO" Bau7SroJTlO) sample" ",ere prepared by mixing high purity lllUlOpowders (100nm) of RaTiO) and SrTiOJ together, Mixed powders were pressed into pellets with pre"sures of 300,450 and 600MPa. Ncxt the green samples were dried and then sintered at1200' C, 1225'C and 1250"C temperatures in a muffle furnace, Sintering temperatures & time were vaned to ach'e"e more than 90% of theoretical density. Heating rate "'as also \'aried and fa8ler firing was applied to obtain finc grain size, For pure BaTIO) samples, faster firing re,u1ted in reduced grain sizc and inhibition of ilhnonnal grain growth But lor Ba,.,Sr,TiO) samples, increase in heating rate caused the samples to crack. Microstructural featlIre<,such as grain size and presence of second phase etc were revealed WIth scanning electron minoscope, Phase transitIOn temperatures of sintered samples were detected using diffel'ential scanning calonmetry (DSC). Dlelednc pmperties of sintered samples were measured with an impedance analYler (IoCR meteT) at several t'requcncies e.g. 1KHz; 10KHz, 100KH/ and 1000KHz within the temperature range of 30" to 170'C. Curie point of BaTiO) samples were fOlinu at near 125°C by both DSC technique and LCR meter. It w~s found thaI m~rea,e In grain sizc shilis the Curie point to slightly higher temperature and pha'Se lran.<,ltion peak becomes sharpeI', For Ba,.,Sr,TiOI samples, Curie temperature decreases linearly with increasing value of x, Moreover the frequency dependent dielednc constant and loss tangent were examined at room temperature for BaTiO) and Bal.,Sr,T,O) samples. Samples containing less amount of pores showed mlmmum dielectric loss.