Minimization of pyroelectric effects in relaxor-PbTiO3 crystals for piezoelectric sensors

To minimize pyroelectric effects while keeping high piezoelectric effects in relaxor-PbTiO3 single crystals, the crystallographic orientation dependence of the pyroelectric and piezoelectric coefficients were investigated for binary (1 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), ternary (1 − x − y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT) and Mn-doped PIN-PMN-PT single crystals with the “4R” multidomain state. The secondary pyroelectric coefficients were calculated from the thermodynamic inter-relationship between the piezoelectric, elastic, and thermal expansion coefficients, being on the order of (1.16-1.23) × 10−4 C m−2 K−1 for binary crystals and (0.97-2.03) × 10−4 C m−2 K−1 for ternary ones. The primary pyroelectric coefficients were -(6.73-6.84) × 10−4 C m−2 K−1 and −(5.44-6.43) × 10−4 C m−2 K−1 for binary and ternary crystals, respectively. The pyroelectric coefficients could be reduced by matrix rotation, but at the cost of decreasing longitudinal piezoelectric coefficients d33. Of particular interest is that the maximum piezoelectric coefficients d24∗ at θ = ±55o and d34∗ at θ = ±35o by a counterclockwise rotation of θ about the X axis (θ is the rotation angle about the coordinate axes), or d15∗ at θ = ±55o, and d35∗ at θ = ±35o by a counterclockwise rotation the Y axis, were found on the order of 3000 pC N−1. The corresponding pyroelectric coefficients could be reduced by ∼20%. The reduced pyroelectric coefficients that can contribute to decrease undesirable output signals, together with the high piezoelectric coefficients, enable relaxor-PT crystals as favorable candidates for high-sensitivity piezoelectric sensors.