| || Modified Lead-zirconate-titanate for Pyroelectric Sensors
Author : Thakur, O. P.;Singh, J. P.;Prakash, Chandra;Pran Kishan
Source : Defence Science Journal ; Vol:57(3) ; 2007 ; pp 233-239
Subject : 681.586 Sensors
Keywords : PZT;IR detectors;Ceramic materials;Lead-zirconatetitanate systems;Pyroelectric sensors;Sensors
Abstract : Pyroelectric sensors based on ceramic materials have found applications in IR detection in defence and civil systems. To develop suitable ceramic material for IR detector applications, a modified PZT system with compositional formula Pb1-xSmx(Zr0.58Fe0.18Mn0.02Nb0.2Ti0.02)O3 where 0 £ x £ 0.025 was synthesised by conventional solid state reaction method. The materials were characterised for their properties like dielectric and pyroelectric coefficient. Hysteresis loop was recorded at room temperature. The sample with 2 mole per cent samarium (Sm) substitutions was found to be more promising for sensor application based on its high material's figure of merit (FOM). Sensors fabricated with this material were integrated with FET amplifier. The devices configured with compensating element were evaluated for different chopping frequencies. The value of material's FOM, FD, and detectivity, D*, were determined from measured parameters and were, 3.6 x 10-5 Pa-1/2 and 2 x 108 cmHz1/2/W, respectively.
| || Synthesis structural and electrical properties of Lanthanum modified Lead zirconate titanate system
Author : Singh, Sarabjit;Thakur, O. P.;Chandra Prakash,
Source : Defence Science Journal ; Vol:55(3) ; 2005 ; pp 349-355
Subject : 620.1 Material Science and Technology
Keywords : Ceramics;Lead zirconate titanate ceramics;PZT;Ferroelectric behaviour;Piezoelectric charge coefficient;PLZT;Rhombohedral structure;Lanthanum substituted PZT ceramics
Abstract : Lead-zirconate-titanate (PZT) ceramics with zirconate-titanate (65:35) have been synthesised with the substitution of lanthanum (6, 7 and 8 mol%). Samples were prepared by solid-state reaction route. The x-ray diffraction study shows the formation of a single phase with rhombohedral structure. There is a transformation in crystal structure from tetragonal to co-existence of tetragonal, and rhombohedral to a single rhombohedral phase with the increase in the lanthanum concentration in the basic PZT composition. Results of a detailed dielectric study indicate the diffuse-phase transition at higher values of lanthanum concentration, which may be attributed to the microscopic heterogeneity in the composition. Dielectric properties of the poled and unpoled samples have also been compared and found that the values decreased after poling. Ferroelectric hysteresis behaviour was also studied as a function of temperature for all the three compositions, which showed typical variation of ferroelectric nature. Piezoelectric charge coefficient (d33) decreases with increase in the lanthanum and with the increase of frequency as well, up to the measured limit.
| || Effect of Sintering Temperature on Structural and Piezoelectric Properties of PNN-PZT Ceramics
Author : Mahajan, Sandeep;Thakur, O. P.;Prakash, Chandra
Source : Defence Science Journal ; Vol:57(1) ; 2007 ; pp 23-28
Subject : 66 Chemical Technology
Keywords : PNN-PZT ceramics;Piezoelectric properties;Dielectric properties;Sintering temperature;Piezoelectric ceremics;Piezoelectric materials;Mechanical activation;Perovskite phase
Abstract : Sintering temperatures affect the structural and piezoelectric properties of PbNi1/3Nb2/3- PbZrO3-PbTiO3 system considerably; therefore the effect has been studied on mechano-chemically processed powder. This process involves activating mixed oxides of PbO, NiO, Nb2O5, ZrO2 and TiO2, and in the present study, calcination steps at an intermediate temperatures were skipped which are usually required in conventional solid state reaction methods and chemical routes. Single-phase formation was confirmed from XRD patterns which shows rhombohedral structure at higher sintering temperature. Investigations of the microstructure indicate almost linear increase in grain size from 0.98 m to 2.56 m when the sintering temperature was varied from 1050 oC to 1150 °C. A high value of planar coupling factor (kp) = 67 per cent and piezoelectric charge coefficient (d 33 ~ 750 pm/V; (as determined from strain versus electric field curve at low field) were obtained for the ceramic specimens sintered at 1100 °C. The maximum strain was observed ~ 0.21 per cent at 40 kV/cm applied field for the sample sintered at 1100 °C for 4 h.